Object lens for optical pickup, optical pickup and optical information processing device

ABSTRACT

As an object lens for an optical pickup, applied is a single-lens and both-side-convex configuration is applied. Further, specific conditional formulas are created with respect to a particular numerical aperture NA, for a paraxial curvature radius R 1  on the surface on the light source side; the working distance WD, the refractive index nd with respect to the d-line, and the focal length f. Furthermore, specific conditional formulas are created for the refractive index nd with respect to the d-line and the Abbe&#39;s number νd.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object lens for an optical pickup,an optical pickup, and an optical information processing device.

2. The Description of the Related Art

For “an optical recording medium” such as a CD (compact disk) or a DVD(digital video disk), “an optical information processing device” whichperforms recording, reproduction, and deletion of information using anoptical pickup has been spread widely. In this technical field,high-density recording onto the optical recording medium is demanded.

Since the light spot formed on the recording surface of the opticalrecording medium is formed of a beam waist of a laser beam whichconverges by means of the object lens of the optical pickup, and thediameter of the beam waist is proportional to the wavelength of laserbeam, and, also, is inverse proportional to the numerical aperture (NA)of the object lens, increase in NA of the object lens in the opticalpickup and shortening in the wavelength of laser beam are demandedaccordingly.

As to the shortening of the wavelength of laser beam, a semiconductorlaser having “the emission wavelength around 660 nm” for DVD is alreadyput in practical use, and, these days, a laser light source having thewavelength around 400 nm is also being put in practical use.

As the object lens having the large NA exceeding 0.7 has been proposed(for example, see Japanese laid-open patent application No. 10-123410).However, any of such object lenses having the large NA has atwo-lens-combined configuration. Compared with a single-lensconfiguration, such a type of lens of two-lens-combined configurationrequires complicated assembling process, high precision in assemblingwork, and, also, may not be driven at a high speed due to increase inthe weight itself.

Moreover, as a working distance, i.e., the distance between the objectlens and the optical recording medium surface is shortened in case ofemploying such a two-lens-combined configuration, there increases a riskof hitting of the object lens onto the recording medium surface,resulting in a series damage occurring thereon. As a result, it becomesdifficult to achieve high reliability in this scheme.

Although such a problem does not occur in case of usage of a single lensconfiguration in the object lens, it may not be possible to achievelarge NA. For example, around 6.5 is the maximum on those known.

Conventionally, an incident side substrate thickness, i.e., the distancebetween the surface of the recording medium on which the beam isincident and the recording surface thereof is prescribed as being 1.2 mmfor CD while as being 0.6 mm for DVD. However, recently, a new trendoccurs in which the incident side substrate thickness is to bestandardized into as small as 0.1 mm.

There is a variation for every individual in the emission wavelength ofthe semiconductor laser generally used as the light source of theoptical pickup, and there is also a phenomenon called mode hopping inwhich several nm change in the main wavelength occurs with temperaturechange etc. in the semiconductor laser.

In the optical pickup, when the wavelength emitted from thesemiconductor laser changes from the original design value due to thevariation for every individual, or due to the mode hopping, chromaticaberration arises in the optical pickup's optical system, the diameterof beam spot increases on the medium recording surface, and thus, thereis a possibility of causing a problem on recording/reproducing operationin the device.

Especially the chromatic aberration occurring in the object lens by thewavelength change when using the short wavelength semiconductor lasernot more than the emission wavelength around 440 nm may causes anonpermissible problem. Namely, the refractive-index change with respectto a minute wavelength change becomes large in such a short wavelengthrange, and also, the chromatic aberration becomes large and the amountof defocus which is the focal movement amount becomes large.Furthermore, the beam spot on the recording medium is shortened so as toachieve high density recording, and, also, the focal depth of the objectlens is proportional to the wavelength and inverse proportional to thesecond power of NA. Accordingly, the focal depth becomes smaller as thewavelength is shorter, and, thus, the tolerance on the defocus becomesrestricted.

On the other hand, manufacture error on the order of ±10 nm is notavoidable with respect to the incident side substrate thickness of 0.1mm. Such a substrate thickness error may cause spherical aberration inimaging function of the object lens designed according to thestandardized substrate thickness. Thereby, the beam spot diameter may beincreased, and, thus, the proper operation may not be expected in theoptical pickup. As well-known, the spherical aberration is proportionalto the forth power of NA of the object lens, the substrate thicknesserror may cause a larger problem as NA of the object lens increases.

As the optical recording medium, recently, in order to achieve a largerecording capacity, a so-called “multilayer optical recording medium” inwhich a plurality of recording layers are placed on each other in asingle recording disk has been put in practical use. In such amultilayer optical recording medium, since the recording surfaceseparation (space thickness) of several 10 micrometers or more is neededand the distance from the object lens is different for every recordingsurface when recording, reproduction, or deletion of information isperformed independently onto the respective ones of the plurality ofrecording surfaces. Accordingly, the spherical aberration may occur on arecording surface thereof different from the optimum position.

In the semiconductor laser used as the light source, utilization of thesemiconductor laser with an oscillation wavelength around 400 nm hasbeen attained. As the high NA lens, the high NA lens for the pickupwhich includes an aspheric surface lens of two-lens-combinedconfiguration is disclosed in Japanese laid-open patent applicationsNos. 2001-83410, 11-202194, and 11-203711. However, as described above,such a two-lens-combined configuration object lens even having high NAmay be problematic in comparison to a single lens configuration.

Japanese laid-open patent application No. 2001-324673 discloses anobject lens beyond NA: 0.7 of single lens configuration solving theabove-mentioned problem.

However, these conventional examples have a low implementability interms of manufacture. In fact, in order for the object lens of singlelens configuration to attain a raise in NA, and shortening theapplicable wavelength, it is necessary to select such a type of glassmaterial that press fabrication thereof can be made using a die havingultra-precision machining performed thereon, it is necessary to achievesatisfactory wavefront performance at a design median, and, also, it isnecessary to make the manufacture tolerance to fall within a range ofimplementability. Specifically, first, as to the wavefront aberration inthe design median, it should be controlled less than 0.01λ.

According to the inventor's calculation, the wavefront aberration of theobject lens for an optical pickup disclosed by Japanese laid-open patentapplication No. 2001-324673, embodiment 3 should be 0.037λ, and thus, wecould say that implementality is low, where this object lens is used forthe wavelength of 400 nm, has NA: 0.85, and f (focal length): 1.765 mm,nd (refractive index in the lens material with respect to the d-line):1.71667, and νd (number of Abbe in the lens material with respect to thed-line): 53. Moreover, actual utilization thereof is difficult when theimplementability on the condition of the manufacture tolerance is loweven when the wavefront performance in the design median issatisfactory. For example, the wavefront aberration needs to fall on theorder of not more than 0.015λ with respect to the deviation in thethickness more than ±1 μm. FIG. 1 shows a relationship between thethickness tolerance and wavefront aberration on the object lens foroptical pickup used in the wavelength: 650 nm, having NA: 0.75, f: 2.00mm, nd: 1.69330, and νd: 53, as another example. As can be seentherefrom, the above-mentioned conditions cannot be actually satisfied.

Therefore, it is demanded to provide a lens with a reduced amount inwavefront performance degradation with respect to the manufacturetolerance, or to provide an optical pickup which can control the amountin wavefront performance degradation with respect to the manufacturetolerance.

Moreover, while the new standard of increasing NA and shortening theapplied wavelength will be issued near future, there exist theconventional CD and DVD. It is preferable that these conventionaloptical recording media and the optical recording media according to theabove-mentioned new standard can both be dealt with by a common opticalinformation processing device. As an easier method therefor, aconventional optical pickup and an optical pickup according to the newstandard are both mounted in one information processing device. However,it is difficult to attain a miniaturization and cost reduction of thedevice according to such a scheme.

SUMMARY OF THE INVENTION

In view of the above-described situation, the present invention has anobject of achieving the object lens of a single lens configuration,which is advantageous for forming a small-sized beam spot and, also,having a large NA, which object lens is also advantageous in applicationinto the optical pickup and the optical information processing device.

Another object of the present invention is to well control the chromaticaberration caused by the operating wavelength change/variation, and toraise accuracy in operation of the optical pickup which uses this objectlens.

Another object of the present invention is to well correct the sphericalaberration caused by the substrate thickness error, so as to raise thereliability of the optical pickup.

Another object of the present invention is to achieve satisfactoryrecording, reproduction, or deletion onto each recording surface of themultilayer optical recording medium in the optical pickup which uses theabove-mentioned object lens.

According to the present invention, as the object lens for the opticalpickup, a single-lens and both-side-convex configuration is applied.Further, a number of specific conditional formulas are created withrespect to a particular numerical aperture NA, for a paraxial curvatureradius R1 on the surface of the lens on the light source side; theworking distance WD, the refractive index nd with respect to the d-line,and the focal length f. Furthermore, specific conditional formulas arecreated for the refractive index nd with respect to the d-line and theAbbe's number νd with respect to the d-line.

Thereby, as the single-lens configuration is applied, it is possible toavoid increase in the number of components, increase in the totalweight, difficulty in achievement of required assembling accuracy, andso forth in the pickup applying the object lens. Furthermore, it becomespossible to achieve the numerical aperture of 6.5 or more, and also, toemploy the short operating wavelength of 650±20 nm or 407±10 nm, and,thereby, to achieve an advantageous small light spot or beam spot on therecording surface, positively.

By applying such a high-performance object lens for the optical pickup,the pickup can be suitably supplied for high-density informationrecording. Accordingly, by applying the optical pickup in an opticalinformation processing device, it is possible to perform recording,reproducing and deleting of information on each type of opticalrecording medium required, with a satisfactory recordingcondition/performance.

Another object of the present invention is to solve the above-mentionedproblems, and, to provide an object lens for an optical pickup having alarge NA thereby advantageous in effective reduction in the light spotdiameter, and, also, has a large manufacture tolerance, wherein, withoutmounting a plurality of optical pickups, it is possible to deal with notonly an optical recording media according to the new standard but alsoconventional CD and DVD, and also, to well correct aberration evenincreased due to a possible manufacture error, so as to improve thereliability in the optical pickup.

According to another aspect of the present invention, as the object lensfor the optical pickup, a single-lens and both-side-convex and alsoboth-side aspherical configuration formed in a glass-mode manner isapplied. Also in this case, a number of specific conditional formulasare created with respect to a particular numerical aperture NA, for aparaxial curvature radius R1 on the surface of the lens on the lightsource side, the working distance WD, the refractive index nd withrespect to the d-line, and the focal length f. Furthermore, specificconditional formulas are created for the refractive index nd withrespect to the d-line and the Abbe's number νd with respect to thed-line.

Other objects and further features of the present invention will becomemore apparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a relation between lens thickness error and wavefrontaberration in an object lens in the related art;

FIGS. 2A, 2B and 2C show a shape, astigmatism and spherical aberrationof an embodiment 1 of the present invention;

FIGS. 3A, 3B and 3C show a shape, astigmatism and spherical aberrationof an embodiment 2 of the present invention;

FIGS. 4A, 4B and 4C show a shape, astigmatism and spherical aberrationof an embodiment 3 of the present invention;

FIGS. 5A, 5B and 5C show a shape, astigmatism and spherical aberrationof an embodiment 4 of the present invention;

FIGS. 6A, 6B and 6C show a shape, astigmatism and spherical aberrationof an embodiment 5 of the present invention;

FIGS. 7A, 7B and 7C show a shape, astigmatism and spherical aberrationof an embodiment 6 of the present invention;

FIGS. 8A, 8B and 8C show a shape, astigmatism and spherical aberrationof an embodiment 7 of the present invention;

FIGS. 9A, 9B and 9C show a shape, astigmatism and spherical aberrationof an embodiment 8 of the present invention;

FIGS. 10A, 10B and 10C show a shape, astigmatism and sphericalaberration of an embodiment 9 of the present invention;

FIGS. 11A, 11B and 11C show a shape, astigmatism and sphericalaberration of an embodiment 10 of the present invention;

FIGS. 12A, 12B and 12C show a shape, astigmatism and sphericalaberration of an embodiment 11 of the present invention;

FIGS. 13A, 13B and 13C show a shape, astigmatism and sphericalaberration of an embodiment 12 of the present invention;

FIG. 14 shows a specification of the embodiment 1;

FIG. 15 shows a specification of the embodiment 2;

FIG. 16 shows a specification of the embodiment 3;

FIG. 17 shows a specification of the embodiment 4;

FIG. 18 shows a specification of the embodiment 5;

FIG. 19 shows a specification of the embodiment 6;

FIG. 20 shows a specification of the embodiment 7;

FIG. 21 shows a specification of the embodiment 8;

FIG. 22 shows a specification of the embodiment 9;

FIG. 23 shows a specification of the embodiment 10;

FIG. 24 shows a specification of the embodiment 11;

FIG. 25 shows a specification of the embodiment 12;

FIG. 26 illustrates an optical pickup according to one embodiment of thepresent invention;

FIGS. 27A, 27B and 27C illustrate an optical pickup according to anotherembodiment of the present invention;

FIGS. 28A and 28B illustrate an optical pickup according to anotherembodiment of the present invention;

FIGS. 29A through 29D illustrate an optical pickup according to anotherembodiment of the present invention;

FIG. 30 shows an optical pickup according to another embodiment of thepresent invention;

FIG. 31 illustrates an optical recording medium having a plurality ofrecording surfaces stacked on each other;

FIG. 32 shows an internal perspective view of an optical informationprocessing device according to an embodiment of the present invention;

FIGS. 33, 34, and 35A through 35F illustrate conditional formulas forthe object lens according to the present invention;

FIG. 36 shows lens materials in relation with refractive index andAbbe's number thereof;

FIGS. 37A through 37C illustrate other conditional formulas of theobject lens according to the present invention;

FIGS. 38A through 38D illustrate an embodiment 13 of the presentinvention;

FIGS. 39A through 39D illustrate an embodiment 14 of the presentinvention;

FIG. 40 shows a specification of the embodiment 13;

FIG. 41 shows a specification of the embodiment 14;

FIGS. 42A and 42B illustrate other conditional formulas according to thepresent invention;

FIGS. 43A and 43B illustrate an embodiment 15 of the present invention;

FIGS. 44A and 44B illustrate an embodiment 16 of the present invention;

FIG. 45 shows a specification of the embodiment 15;

FIG. 46 shows a specification of the embodiment 16;

FIG. 47 illustrates an embodiment 17 of the present invention;

FIGS. 48A through 48C illustrate an embodiment 18 of the presentinvention;

FIGS. 49A and 49B illustrate an embodiment 19 of the present invention;

FIG. 50 illustrates an embodiment 20 of the present invention;

FIGS. 51A through 51E illustrate a state of wavefront aberrationcorrection according to the embodiment 20;

FIGS. 52A and 52B illustrate an embodiment 21 of the present invention;

FIGS. 53A and 53B illustrate a state of wavefront aberration correctionaccording to the embodiment 21;

FIG. 54 illustrates an embodiment 22 of the present invention;

FIGS. 55A through 55E illustrate a state of wavefront aberrationcorrection according to the embodiment 22;

FIGS. 56A and 56B illustrate an embodiment 23 of the present invention;

FIGS. 57A and 57B illustrate a state of wavefront aberration correctionaccording to the embodiment 23; and

FIG. 58 illustrates an internal perspective view of an informationprocessing device in another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Specific embodiments of an object lens for an optical pickup accordingto the present invention will now be described. In each of FIGS. 2A, 3A,. . . , 13A, a reference numeral “1” stands for an aperture, “2” standsfor the object lens for an optical pickup according to the presentinvention, and “3” stands for an incident side substrate of an opticalrecording medium (having the thickness of 0.1 mm).

A laser beam emitted from a light source passes through an opening(having a diameter of 3 mm) of the aperture 1, is incident on the objectlens 2, the beam becomes a condensing beam by means of this lens 2, theincident side substrate 3 of the optical recording medium is passedthrough by the condensing beam, and then, a light spot is formed on arecording surface RS of the optical recording medium.

Twelve embodiments of the present invention, i.e., embodiments 1 through12 will now be described. In each of the embodiments 1, 3, 5, 7, 9, and11, the object lens for the optical pickups is a meniscus lens having aconvex surface facing the light source side, while, in each of theembodiments 2, 4, 6, 8, 10, and 12, the object lens for the opticalpickup is both-side-convex lens with a surface having a radius ofcurvature smaller (sharper curvature) facing the light source side.

For each embodiment, the refractive index with respect to the d-line andthe number of Abbe with respect to the d-line of the lens material arereferred to as nd and νd, respectively, the numerical aperture isreferred to as NA, and the focal length is referred to as f.

The aspherical shape on the lens surface is expressed by the followingwell-known formula:X=(Y ² /R)/[1+√{square root over ( )}{1−(1+K)(Y/R)² }+AY ⁴ +BY ⁶ +CY ⁸+DY ¹⁰ +EY ¹² +FY ¹⁴ +GY ¹⁶ +HY ¹⁸ +JY ²⁰+ . . .where X stands for the coordinates along the optical axis, Y stands forthe coordinates along a direction perpendicular to the optical axis, Rdenotes the paraxial curvature radius, K denotes a cone constant, A, B,C, D, E, F, . . . stand for high-order coefficients, and R, K, A, B, C,D, . . . are given so as to express the particular aspherical surface.

Embodiment 1

The object lens for the optical pickup in the embodiment 1 is used withthe operating wavelength of 650 nm. Further, this lens has the followingspecification:

NA: 0.65, f: 2.31 mm, nd=1.74330, and νd=49.36. The other specific datais show in FIG. 14.

In the table shown in FIG. 14, “OBJ” stands for an object point (asemiconductor laser as a light source). The object lens for the opticalpickup is according to “infinite system”. Accordingly, “INFINITY”mentioned in the item of each of the curvature radius RDY and thicknessTHI means that the light source is located at the infinite distantpoint. “STO” stands for a surface of the aperture 1, and, the curvatureradius RDY is set to “INFINITY”, and the thickness thereof is set to “0”on the design. In the description of the embodiments, the unit of amounthaving a dimension of length is “mm”, hereinafter.

“S1” stands for the “light-source-side surface” of the object lens forthe optical pickup, and “S2” means the “optical-recording-medium-sidesurface” of the same. The thickness of the lens (THI) in the embodiment1 is 2.0000 mm, and the name of glass material (GLA) thereof isNMBF1_HOYA as shown in FIG. 14. Further, 0.831223 mm shown in the figurein the field for S2 at the right hand of the curvature radius indicatesthe working distance, i.e., the distance between theoptical-recording-medium side surface of the object lens and theobject-lens side surface of the incident side substrate of the opticalrecording medium.

“S3” stands for the light-source-side surface of the incident-sidesubstrate 3 of the optical recording medium, while “S4” stands for thesurface corresponding to the recording surface RS of the opticalrecording medium. The distance between S3 and S4, i.e., the thickness ofthe incident-side substrate is 0.1 mm, and, the material thereof ispolycarbonate having the refractive index: n=1.58, as shown. “EPD”(entrance pupil diameter) shown expresses the diameter (3 mm) of theopening of the aperture 1, and “WL” (wavelength) expresses the operatingwavelength (650 nm), in FIG. 14.

In the fields of S1 and S2, for example, “D: −0.625230E-04” means“D=−0.625230×10⁻⁴”, indicating the coefficient D of the formula for theaspherical surface. The same manner is also applied in the descriptionof every embodiment.

FIG. 2A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 1. FIGS. 2B and 2C showthe astigmatism and the spherical aberration of the object lens in theembodiment 1, where the scale on the vertical axis indicates the valuenormalized in a manner such that the entrance pupil radius is made to be1). As can be seen there, both the aberrations are corrected verysatisfactorily. In fact, “wavefront aberration” is less than 0.01λ.

As mentioned above, according to the embodiment 1, R1=1.68376 mm, f=2.31mm, nd=1.74330, and the number of Abbe νd=49.36 and the working distance(WD)=0.831223 mm. Accordingly, R1, f, and nd satisfy the conditions ofthe following formulas (1) and (2), and, also, both the refractive indexand the number of Abbe satisfy the conditions of the following formulas(3) and (4):1.2nd−1.1<R1/f≦1.3nd−1.2  (1)0.37nd−0.14<WD/f≦0.39nd−0.04  (2)νd≦60  (3)1.5≦nd  (4)

Embodiment 2

An object lens for an optical pickup according to the embodiment 2 ofthe present invention is an example used with the operating wavelength:650 nm. Further, NA: 0.65, f: 2.31 mm, nd=1.58313, and νd=59.46. Theother specific data is shown in FIG. 15 in the manner same as that ofFIG. 14.

FIG. 3A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 2. FIGS. 3B and 3C showthe astigmatism and the spherical aberration of the object lens in theembodiment 2, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen there, both the aberrations arecorrected very satisfactorily. In fact, “wavefront aberration” is lessthan 0.01λ.

As mentioned above, according to the embodiment 2, R1=1.47611 mm, f=2.31mm, nd=1.58313, and the number of Abbe νd=59.46 and working distance(WD)=1-0.096024 mm. Accordingly, R1, f, and nd satisfy the conditions ofthe above-mentioned formulas (1) and (2), and, also, both the refractiveindex and the number of Abbe νd satisfy the conditions of theabove-mentioned formulas (3) and (4).

Embodiment 3

An object lens for an optical pickup according to the embodiment 3 ofthe present invention is an example to be used with the operatingwavelength: 650 nm. Further, NA: 0.75, f: 2.00 mm, nd=1.74330, andνd=49.36. The other specification is shown in FIG. 16.

FIG. 4A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 3. FIGS. 4B and 4C showthe astigmatism and the spherical aberration of the object lens in theembodiment 3, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen there, both the aberrations arecorrected very satisfactorily. In fact, “wavefront aberration” is lessthan 0.01λ.

According to the embodiment 3, R1=1.45407 mm, f=2.00 mm, and nd=1.74330,the number of Abbe: νd=49.36 and working distance (WD)=0.585206 mm.Accordingly, R1, f, and nd satisfy the conditions expressed by thefollowing formulas (5) and (6), and both the refractive index and thenumber of Abbe satisfy the conditions of the following formulas (7) and(8):1.0nd−0.7<R1/f≦1.2nd−1.1  (5)0.33nd−0.18<WD/f≦0.37nd−0.14  (6)νd≦60  (7)1.6≦nd  (8)

Embodiment 4

An object lens for an optical pickup according to the embodiment 4 ofthe present invention is an example used with the operating wavelength:650 nm, and has the following specification: NA: 0.75, f: 2.00 mm,nd=1.69330, and νd=53.17. The other data is shown in FIG. 17, in thesame manner as that on FIG. 14.

FIG. 5A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 4. FIGS. 5B and 5C showthe astigmatism and the spherical aberration of the object lens in theembodiment 4, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01.

According to the embodiment 4, R1=1.50153 mm, f=2.00 mm, nd=1.69330, theAbbe number: νd=53.17 and the working distance (WD)=0.849168 mm.Accordingly, R1, f, and nd satisfy the conditions of the above-mentionedformulas (5) and (6), and both the refractive index and the Abbe numbersatisfy the conditions shown in the above mentioned formulas (7) and(8).

Embodiment 5

An object lens for an optical pickup according to the embodiment 5 is anexample also used with the operating wavelength: 650 nm, and has thefollowing specification: NA: 0.85, f: 1.76 mm, nd=1.74330, and νd=49.36.The other specification is shown in FIG. 18 in the same manner as thatin FIG. 14.

FIG. 6A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 5. FIGS. 6B and 6C showthe astigmatism and the spherical aberration of the object lens in theembodiment 5, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 5, R1=1.2997 mm, f=1.76 mm, nd=1.743, Abbe'snumber: νd=49.36, and the working distance (WD)=0.465294 mm.Accordingly, R1, f, and nd satisfy the conditions expressed by thefollowing formulas (9) and (10). Further, both the refractive index andthe Abbe's number satisfy the conditions expressed by the followingformulas (11) and (12):R1/f≦1.0nd−0.7  (9)WD/f≦0.33nd−0.18  (10)30≦νd≦50  (11)1.65≦nd≦1.80  (12)

Embodiment 6

An object lens for an optical pickup according to the embodiment 6 isused with the operating wavelength: 650 nm, and has the followingspecification: NA: 0.85, f: 1.76 mm, nd=1.69330, and νd=53.17. The otherspecification is shown in FIG. 19.

FIG. 7A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 6. FIGS. 7B and 7C showthe astigmatism and the spherical aberration of the object lens in theembodiment 6, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 6, R1=1.2977 mm, f=1.76 mm, nd=1.69330, theAbbe's number: νd=53.17 and the working distance (WD)=0.591052 mm.Accordingly, R1, f and nd satisfy the conditions of the above-mentionedformulas (9) and (10), and also, both the refractive index and Abbe'snumber satisfy the conditions of the above-mentioned formulas (11) and(12).

Embodiment 7

An object lens for an optical pickup according to the embodiment 7 isused with the operating wavelength: 407 nm, and has the followingspecification: NA: 0.65, f: 2.31 mm, nd=1.74330, and νd=49.36. The otherspecification is shown in FIG. 20.

FIG. 8A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 7. FIGS. 8B and 8C showthe astigmatism and the spherical aberration of the object lens in theembodiment 7, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 7, R1=1.71822 mm, f=2.31 mm, nd=1.74330,Abbe's number: νd=49.36, and the working distance (WD)=0.831223, asshown. Accordingly, R1, f and nd satisfy the following formulas (13) and(14), while both the refractive index and the Abbe's number satisfy thefollowing formulas (15) and (16):1.2nd−1.1<R1/f≦1.3nd−1.2  (13)0.37nd−0.14<WD/f≦0.39nd−0.04  (14)νd≦60  (15)1.5≦nd  (16)

Embodiment 8

An object lens for an optical pickup in the embodiment 8 is used withthe operating wavelength: 407 nm, and has the following specification:NA: 0.65, f: 2.31 mm, nd=1.58313, and νd=59.46. The other specificationis shown in FIG. 21.

FIG. 9A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 8. FIGS. 9B and 9C showthe astigmatism and the spherical aberration of the object lens in theembodiment 8, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 8, R1=1.52938 mm, f=2.31 mm, nd=1.58313,Abbe's number: νd=59.46, and the working distance (WD)=1.115081 mm, asshown. Accordingly, R1, f and nd satisfy the above-mentioned conditionalformulas (13) and (14), and both the refractive index and the Abbe'snumber satisfy the above-mentioned conditional formulas (15) and (16).

Embodiment 9

An object lens for optical pickup according to the embodiment 9 is usedwith operating wavelength: 407 nm, and has the following specification:NA: 0.75, f: 2.00 mm, nd=1.74330, and νd=49.36. The other specificationis shown in FIG. 22.

FIG. 10A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 9. FIGS. 10B and 10Cshow the astigmatism and the spherical aberration of the object lens inthe embodiment 9, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 9, R1=1.48011 mm, f=2.00 mm, nd=1.74330, theAbbe number: νd=49.36 and the working distance (WD)=0.583068 mm.Accordingly, R1, f and nd satisfy the following conditional formulas(17) and (18), while both the refractive index and the Abbe numbersatisfy the following continual formulas (19) and (20):1.0nd−0.7<R1/f≦1.2nd−1.1  (17)0.33nd−0.18<WD/f≦0.37nd−0.14  (18)νd≦60  (19)1.6≦nd≦1.8  (20)

Embodiment 10

An object lens for optical pickup according to the embodiment 10 is usedin the operating wavelength: 407 nm, and has the followingspecification: NA: 0.75, f: 2.00 mm, nd=1.69330, and νd=53.17. The otherspecification is shown in FIG. 23.

FIG. 11A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 10. FIGS. 11B and 11Cshow the astigmatism and the spherical aberration of the object lens inthe embodiment 10, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 10, R1=1.56813 mm, f=2.00 mm, nd=1.69330,the Abbe's number: νd=53.17 and the working distance (WD)=0.874666 mm.Accordingly, R1, f, and nd satisfy the above-mentioned conditionalformulas (17) and (18), while both the refractive index and the Abbe'snumber satisfy the above-mentioned conditional formulas (19) and (20).

Embodiment 11

An object lens for an optical pickup according to the embodiment 11 isused in the operating wavelength: 407 nm, and has the followingspecification: NA: 0.85, f: 1.76 mm, nd=1.74330, and νd=49.36. The otherspecification is shown in FIG. 24.

FIG. 12A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 11. FIGS. 12B and 12Cshow the astigmatism and the spherical aberration of the object lens inthe embodiment 11, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 11, R1=1.33386 mm, f=1.76 mm, nd=1.74330,the Abbe's number: νd=49.36, and the working distance (WD)=0.468034 mm.Accordingly, R1, f, and nd satisfy the following conditional formulas(21) and (22). Further, as the Abbe's number satisfies the followingconditional formula (23), while the refractive index nd does not satisfythe following conditional formula (24), and higher than the conditionalrange:R1/f≦1.0nd−0.7  (21)WD/f≦0.33nd−0.18  (22)45≦νd≦55  (23)1.65≦nd≦1.72  (24)

Thus, as the meniscus lens is used, although the performance issatisfactory as the wavefront aberration: 0.01λ according to theembodiment 11, it is possible to use the lens material having therefractive index higher than the above-mentioned conditional range ofthe formula (24).

Embodiment 12

An object lens for an optical pickup according to the embodiment 12 isused in the operating wavelength: 407 nm, and has the followingspecification: NA: 0.85, f: 1.76 mm, nd=1.69330, and νd=53.17. The otherspecification is shown in FIG. 25.

FIG. 13A shows an arrangement of the aperture 1, the object lens 2, andthe incident side substrate 3 in the embodiment 12. FIGS. 13B and 13Cshow the astigmatism and the spherical aberration of the object lens inthe embodiment 12, respectively, where the scale on the vertical axisindicates the value normalized in a manner such that the entrance pupilradius is made to be 1. As can be seen therefrom, both the aberrationsare corrected very satisfactorily. In fact, “wavefront aberration” isless than 0.01λ.

According to the embodiment 12, R1=1.35305 mm, f=1.76 mm, nd=1.69330,the Abbe number: νd=53.17 and the working distance (WD)=0.615244 mm.Accordingly, R1, f, and nd satisfy the above-mentioned conditionalformulas (21) and (22), while both the refractive index and the Abbe'snumber satisfy the above-mentioned conditional formulas (23) and (24).

Embodiments of an optical pickup according to the present invention willnow be described. FIG. 26 shows one embodiment of the optical pickupwhich includes a chromatic aberration correcting device for correctingchromatic aberration occurring due to wavelength variation. As shown inthe figure, this optical pickup includes a semiconductor laser 4, acollimator lens 5, a polarization beam splitter 6, a deflection mirror7, a ¼-wave plate (quarter wave plate) 9, an object lens 10, a detectionlens 12, a light-receiving device 13, and the chromatic aberrationcorrecting device 14.

A laser beam emitted from the semiconductor laser 4 is changed into asubstantial parallel beam by the collimator lens 5, it passes throughthe polarization beam splitter 6, is bent in its course by 90 degrees bymeans of the deflection mirror 7, and is transformed into a condensingbeam through the chromatic aberration correcting device 14 and theobject lens 10. After that, the beam forms a light spot on a recordingsurface after being incident on an optical recording medium 11 havingthe thickness of 0.1 mm and passing through an incident side substratethereof.

The ¼-wave plate 9 is arranged in front of the object lens 10, andthereby, the linear polarized light coming from the light source istransformed into a circular polarized light. The beam reflected by theoptical recording medium 11 is regarded as a return beam, passes throughthe same course reversely, and then is incident on the polarization beamsplitter 6 through the object lens 10, the ¼-wave plate 9, and thedeflection mirror 7.

The return beam thus incident on the ¼-wave plate 9 is the circularpolarized light different from the state at the time of going process,and, is transformed into a linear polarized light by means of the ¼ waveplate 9 which is perpendicular to the polarized direction in the goingprocess. After that, the beam is reflected by the polarization beamsplitter 6. The return beam reflected by the polarization beam splitter6 is incident on the light-receiving device 13 through the detectionlens 12.

The light-receiving device 13 has a light-receiving surfaceappropriately divided according to a predetermined servo signal creationmethod. Based on the photoelectric output from each light-receivingdivision surface, a tracking signal and a focusing signal are generated,and, at a reproducing process, a reproduction signal is generatedtogether with these signals. These signals are output towards a controlcircuit which is not shown.

The semiconductor laser 4 has the emission wavelength: 650±20 nm, or theemission wavelength: 407±10 nm. As the object lens 10, the object lensaccording to any one of the above-described embodiments of the presentinvention may be used, depending on the emission wavelength and thevignetting factor.

When the emission wavelength of the semiconductor laser 4 deviates fromthe standard wavelength or a wavelength shift occurs due to a modehopping mentioned above, chromatic aberration occurs as mentioned above.The chromatic aberration correcting device 14 corrects such a chromaticaberration.

The chromatic aberration correcting device 14 in the optical pickupshown in FIG. 26 is made of a doublet lens. Specifically, a commonprosaic doublet lens (achromatt lens) known as an achromatic lens, whichis made up of a combination of a convex lens of a crown glass having asmall dispersion and a concave lens of a flint glass having a largedispersion stick together, and controls chromatic aberration, may beused.

On the other hand, the doublet lens 14 as the chromatic aberrationcorrecting device is used mainly for correcting chromatic aberrationoccurring in the object lens 10, and, for this purpose, it provides achromatic aberration having a polarity reverse to that in the objectlens 10. For this purpose, a large difference is created in Abbe'snumber in the optical material between the convex lens and concave lensof the doublet lens 14. Since the chromatic aberration produced by meansof the doublet lens 14 can thus be appropriately enlarged, the chromaticaberration mainly generated in the object lens 10 can be satisfactorilycorrected.

FIG. 27A shows another embodiment of the optical pickup according to thepresent invention which employs another type of a chromatic aberrationcorrecting device. The same reference numerals are given toparts/components same as those shown in FIG. 26, and the duplicateddescription thereof is omitted. In this optical pickup, the chromaticaberration correcting device is integrated with the object lens 10.

The chromatic aberration correcting device 14 a is provided by a glassmaterial, a resin, etc. which has a chromatic aberration of a polarityreverse to that in the object lens 10 and stuck to a surface of theobject lens 10 in the example shown in FIG. 27B. As a resin usedtherein, a photo polymer used as an ultraviolet setting agent or thelike may be applied.

A light spot formed on the optical recording medium 11 can be preventedfrom being influenced by the chromatic aberration, by positivelyproviding an appropriately large difference in Abbe's number (10 ormore) between the above-mentioned optical material (glass material orresin) stuck onto the object lens and the lens material of the objectlens 10 on which the optical material is stuck.

In the example shown in FIG. 27C, the chromatic aberration correctingdevice 14 b is provided as a diffraction surface formed on the objectlens 10. The power of the diffraction surface 14 b formed in a resinfilm united with a lens surface (in this example, on the light sourceside) of the object lens 10 is proportional to the wavelength, and, inthe thus-created positive diffraction lens, as the wavelength becomeslonger, the back focus of the object lens becomes shorter. On the otherhand, since the refractive index of the material falls as the wavelengthbecomes longer in the refraction lens (object lens 10), it has an axialchromatic aberration characteristic in which the back focus is elongatedon a longer wavelength zone. The chromatic aberration correction isattained as a result of the diffraction lens and the refractive lens(object lens) having defocus characteristics reverse to one another.

FIG. 28A shows another embodiment of the optical pickup according to thepresent invention including a substrate thickness error detecting deviceand a spherical aberration correcting device. In the figure, the samereference numerals are given to parts/components same as those shown inFIG. 26, and the duplicated description thereof is omitted.

As the semiconductor laser 4, one having the emission wavelength: 650±20nm, or the emission wavelength: 407±10 nm is used. As the object lens10, the object lens according to any one of the above-describedembodiments of the present invention may be used, depending on theemission wavelength and vignetting factor.

As shown in FIG. 28A, this pickup includes a spherical aberrationdetection device 15 as a substrate thickness error detection device, andthe spherical aberration correcting device 16. As mentioned above, inthe optical recording medium, the standard thickness of the incidentside substrate is 0.1 mm. However, there may occur ‘substrate thicknesserror’ therein in an actually manufactured optical recording medium onthe order of ±10 nm.

Due to existence of such a substrate thickness error, sphericalaberration occurs in a combined system of the object lens 10 and theincident side substrate, and, thereby, the shape of the light spotformed on the recording surface deteriorates. The thus-generatedspherical aberration causes distortion in the wavefront in the returnbeam, and, thereby, causes spherical aberration in the beam directedtoward the light-receiving device 13 through the detection lens 12.

FIG. 28B illustrates this state. When spherical aberration is thusincluded in the return beam being incident onto the detection lens 12from the left hand in the figure, a delay in the wavefront occurs withrespect to the reference wavefront symmetrically with respect to theoptical axis in the return beam. Thereby, a defocus occurs in theposition at which the thus-delayed wavefront is focused with respect tothe focus point at which the reference wavefront is focused.

Then, a situation of wavefront aberration can be known by taking out thedifference between the delayed wavefront and the advanced wavefront, anddetecting the focal state. Specifically, for example, as the sphericalaberration detection device 15 shown in FIG. 28A, a course separationdevice such as a hologram device, a beam splitter, or a device forshifting the timing such as a liquid crystal shutter may be utilized.Further, as shown in FIG. 28B, a light-receiving device 13A divided ininto a light-receiving area A and a light-receiving area B is used.Then, by appropriately processing the light-receiving outputs of theselight-receiving areas A and B, the spherical aberration in the returnbeam can be detected.

The spherical aberration thus detected by means of the sphericalaberration detecting device originates from the substrate thicknesserror in the incident side substrate. Accordingly, by thus detecting thespherical aberration in the return beam, the substrate thickness errorcan be known.

Then, based on the thus-obtained substrate thickness error data, it ispossible to correct the spherical aberration occurring due to thecombination of the object lens 10 and the incident side substrate of theoptical recording medium, and, thereby, to form a proper light spot onthe recording surface of the optical recording medium.

In the embodiment described with reference to FIGS. 28A and 28B, thespherical aberration detected by means of the spherical aberrationdetecting device 15 for the substrate thickness error of the incidentside substrate of the optical recording medium is obtained in a form ofa spherical aberration signal from a combination of the photoelectricsignals from the areas A and B of the light-receiving device 13A.

The spherical aberration correcting device 16 in the embodiment shows inFIG. 28A is provided by two lenses and an interval adjustment device(not shown) to adjust the interval between these lenses. The two lensesare a positive lens and a negative lens. In the figure, the negativelens is disposed on the light source side. However, it is also possiblethat rather the positive lens is disposed on the light source side.

By controlling the separation between the positive lens and negativelens of the spherical aberration correcting device 16, it is possible tocause a spherical aberration in a beam which passes through thespherical aberration correcting device 16 toward the object lens 10.Accordingly, it is possible to use the thus-created spherical aberrationto cancel out the spherical aberration occurring in the combined systemof the object lens 10 and the incident side substrate of the opticalrecording medium.

Specifically, for this purpose, such a separation between the two lensesof the spherical aberration correcting device 16 that theabove-mentioned spherical aberration signal becomes 0 is obtainedbeforehand, and is set as a reference value. Then, when a sphericalaberration occurs actually, the above-mentioned reference separation setbeforehand is adjusted appropriately so that the spherical aberrationsignal becomes 0.

Either one or each of both of the positive lens and negative lens of thespherical aberration correcting device may be made up of a plurality oflenses.

FIGS. 29A through 29E illustrate another embodiment of an optical pickupaccording to the present invention which has a substrate thickness errordetection device and a spherical aberration correcting device. Also inthese figures, the same reference numerals are given to parts/componentssame as those shown in FIG. 26, and the duplicated description thereofis omitted.

The spherical aberration correcting device 16A used in this embodimentincludes a liquid crystal device and a voltage control device (notshown) to drive this. As shown in FIG. 29B, in the liquid crystaldevice, at least one transparent electrode is divided into concentriccircular portions, and, has a configuration such that a voltage can beapplied individually to an electrode portion of each concentric circularportion. Then, it is possible to change the refractive-index n of theliquid crystal on each electrode portion free in a range from n1 throughn2, by controlling the above-mentioned voltage applied.

By thus changing the refractive index n, it is possible to provide anoptical path difference Δn·d to a beam passing through each zone, whereΔn stands for the refractive index change amount, and d stands for thecell thickness of liquid crystal. That is, it is possible to provide aphase difference Δn·d (2π/λ), where λ stands for the operatingwavelength.

It is assumed that the wavefront aberration causes the sphericalaberration generated in the object lens 10 and the incident sidesubstrate in the optical recording medium detected by the sphericalaberration detection device 15 is such as that shown in FIG. 29C. FIG.29D shows this wavefront aberration in a form of a 2-dimensional curve.

Then, by adjusting the voltages applied to the respective concentriccircular zone electrodes of the liquid crystal device so that the phasedifferences shown in the lower half of FIG. 29D are given to the beamincident on the object lens 10 from the side of the light source, it ispossible to cancel out the above-mentioned wavefront aberration, thanksto the delays created in the respective concentric parts of the beampassing through the liquid crystal device. FIG. 29E shows the sum totalof the solid curve (wavefront aberration) and the dashed curve (delay inthe wavefront by the liquid crystal device) in FIG. 29D, i.e., thewavefront aberration after the correction. As can be seen therefrom, thewavefront aberration (the upper half of FIG. 29D) is well corrected.

Thus, a satisfactory light spot can be formed on the recording surfaceof the optical recording medium through correction of theabove-described spherical aberration occurring due to the substratethickness error in the incident side substrate of the optical recordingmedium, by means of the spherical aberration correcting device accordingto each of the embodiments described above with reference to FIGS. 28Athrough 29E.

In addition, the spherical aberration correcting device 16 or 16Adescribed above may preferably perform such a correction operation that:ΔW>|200NA ²+370NA−170|is satisfied where ΔW stands for the change amount of the wavefrontaberration, and NA stands for the numerical aperture of the object lens.Thereby, the quality of the light spot formed can be improved, and thus,quality information recording and information reproduction can beperformed thereby.

The recording surface of the optical recording medium is not restrictedto of one layer. These days, a multilayer optical recording medium asmentioned above is being put into practical use in which many recordingsurfaces are provided in one optical recording medium by means ofconfiguring a multilayer structure therein, and, for each one of themany recording surfaces, recording, reproducing or deletion ofinformation can be made individually. The object lens according to eachembodiment of the present invention described above may also be appliedto an optical pickup in an infinite system applied for such a multilayeroptical recording medium.

In this connection, in the multilayer optical recording medium, it isnecessary to separate several 10 micrometers or more between eachadjacent recording surface in order to perform properly writing andread-out of information individually to/from a plurality of recordingsurfaces of the multilayer optical recording medium. Then, as thedistance to the recording surface on which recording or the like isperformed from the front surface of the optical recording medium thusdiffers for recording or the like performed on a different recordingsurface, unique spherical aberration occurs for every recording surface.

According to an optical pickup in an embodiment according to the presentinvention, in order to perform recording, reproduction, and deletion ofinformation onto a desired recording surface of the multilayer opticalrecording medium, a spherical aberration detection device is providedand detects a spherical aberration amount generated when a focus jump iscarried out into a desired recording surface, and a spherical aberrationcorrecting device is provided and corrects the thus detected sphericalaberration.

FIG. 31 illustrates the above-mentioned multilayer optical recordingmedium 610. As shown in this figure, this optical recording medium 610has an outer surface 601 s through which a beam is incident onrespective recording surfaces 601 a, . . . , 601 n which are provided bymeans of a configuration of multilayer structure thereof. Then, as shownin the figure, a beam 602 a is focused onto the first recording surface601 s, . . . , and a beam 602 n is focused onto the n-th recordingsurface 601 n.

Specific embodiments of an optical pickup having such a multilayeroptical recording medium loaded therein may have configurations the sameas those described above with reference to FIGS. 28A through 29E.

In case where the above-mentioned multilayer optical recording medium isapplied as the optical recording medium 11 in each of the opticalpickups shown in FIGS. 28A and 29A, the spherical aberration amountoccurring when a focus jump is made to a desired recording surface isdetected by the spherical aberration detecting device 15, and, then, thethus-detected spherical aberration is corrected by the sphericalaberration correcting device 16 or 16A.

FIG. 30 shows another embodiment of the optical pickup which uses themultilayer optical recording medium. In the figure, the same referencenumerals are given to parts/components same as those shown in FIG. 26,and the duplicated description thereof is omitted. In FIG. 30, theoptical recording medium 11 is the multilayer optical recording medium,and an object lens 10 is designed so that the wavefront aberrationoccurring when a light spot is formed on a p-th recording surface whichis farthest from the outer surface of the incident side substrate of theoptical recording medium 11 through which a beam after passing throughthe object lens 10 is incident on each recording surface becomes minimumpossible, more preferably, substantially zero. Specifically, in thisembodiment, the distance from the outer surface of the incident sidesubstrate to the p-th recording surface is 0.1 mm.

In this case, since a spherical aberration occurs when a light spot isformed on a q-th recording surface different from the above-mentionedp-th recording surface, the spherical aberration detection device 15detects this spherical aberration, and the spherical aberrationcorrecting device 16B corrects it.

The spherical aberration correcting device 16B in this embodimentincludes a transparent parallel plate having a thickness variesgradually, and a driving device (not shown) to move this transparentparallel plate so as to control the position of this plate at which thebeam coming from the object lens 10 passes through this plate, and thusto control the thickness of this plate to be actually applied to thebeam to be incident onto the optical recording medium through the objectlens 11.

The transparent parallel plate is made up of the material same as thatof the optical recording medium, and has the thickness varying stepwiseeach in a unit of ‘t’ which is the distance between each adjacentrecording layers in the optical recording medium. Then, for example,when recording operation or the like is performed on the q-th recordingsurface, the portion of the transparent parallel plate having thethickness of (p−q)t is inserted between the object lens 10 and theoptical recording medium 11. By performing such a control of thethickness of the transparent parallel plate to be inserted, the totalthickness of the transparent substance inserted between the object lens10 and any recording surface of the optical recording medium 11 can bemade unchanged as the transparent parallel plate compensates thedifference in the distance between the outer surface 601 s and anyrecording surface 601 n. Thereby, distortion of light spot formedoccurring due to spherical aberration can be prevented from occurring,and thus, optimum recording/reproducing can be achieved. The correctionof spherical aberration in the case of performing information recording,etc. to the optical recording medium which has the multiple recordingsurfaces therein may be preferably made so as to satisfy the followingformula:ΔW>|(p−1)t−200NA ²+370NA−170|is satisfied where ΔW stands for the change amount of the wavefrontaberration, and NA stands for the numerical aperture of the object lens.Thereby, the quality of the light spot formed can be improved, and thus,quality information recording and information reproduction can beperformed thereby.

The optical pickups described above with reference to FIGS. 26 through30 are those each of an infinite system performing recording,reproducing or deleting information on the information recording mediumhaving the thickness of the incident side substrate of 0.1 mm. In casethe operating wavelength is 650±20 nm, an object lens according to anyone of the above-described embodiments 1 through 6 is applied. In casethe operating wavelength is 407±20 nm, an object lens according to anyone of the above-described embodiments 7 through 12 is applied.

In the optical pickups described with reference to FIGS. 26 through 27C,each has the chromatic aberration correcting device 14, 14 a, or 14 bfor correcting the chromatic aberration resulting from wavelengthchange. The chromatic aberration correcting device 14 is of a doubletlens including a positive lens in the optical pickup of FIG. 26. Theoptical pickup of FIG. 26A uses the resin coating 14 a provided on theobject lens, or the diffraction surface 14 b.

The optical pickups shown in FIGS. 28A through 31 has the substratethickness error detection device for detecting substrate thickness errorin the incident side substrate of the optical recording medium, and thespherical aberration correcting device 16, 16A and 16B to correctspherical aberration resulting from the substrate thickness error basedon the substrate thickness error which the substrate thickness errordetection device 15 detects. In the optical pickup shown in FIG. 29A,the spherical aberration correcting device 16 is of lens separationvariable, and includes the positive and negative lenses. In the opticalpickup shown in FIG. 30, the liquid crystal device with concentriccircular electrode patterns is utilized.

The optical pickups shown in FIGS. 29A through 30 may also be used in acase where the optical recording medium is of multilayer type, and hasthe thickness of incident side substrate of 0.1 mm. In such a case, theoptical pickup has the spherical aberration detecting device 15 todetect spherical aberration which varies according to the separationbetween the outer surface of the incident side substrate and anyrecording surface, and the spherical aberration correcting device 16 or16A to correct the spherical aberration detected by this sphericalaberration detection device. Then, in case of the operating wavelength:650±20 nm, the object lens which makes the beam from the light sourcecondense as a light spot on a desired recording surface of the opticalrecording medium according to any one of the above-described embodiments1 through 6 may be used. In case the operating wavelength is of 407±10nm, the object lens according to any one of the above-describedembodiments 7 through 12 may be applied for making the beam from thelight source condense as a light spot on the desired recording surfaceof the optical recording medium.

The optical pickups shown in FIGS. 28A through 31 each may have thechromatic aberration correcting device 14, 14 or 14B correctingchromatic aberration occurring due to wavelength change such as thatshown in FIG. 26 or 27A added thereto. Moreover, for example, thefunction as the chromatic aberration correcting device can be providedby applying a glass material having different dispersions to lenses oftwo groups of the spherical aberration correcting device 16 shown inFIG. 28A. That is, it is possible to achieve a single device includingthe functions of both the chromatic aberration correcting device andspherical aberration correcting device together.

FIG. 32 illustrates one embodiment of an optical information processingdevice according to the present invention. The optical informationprocessing device 130 performs recording, reproducing or deletinginformation on an optical recording medium using an optical pickup. Inthis embodiment, the optical recording medium 131 is of a disk, and isheld by a protection case 132. The optical recording medium 131 isinserted into the processing device 130 together with the protectioncase 132, through an insertion mouth 136. After that, the recordingmedium 131 loaded onto a spindle motor 133 is rotated thereby, and,then, recording, reproducing or deleting of information is performed onthe recording medium 131 by means of an optical pickup 135.

As the optical pickup 135, one according to any one of theabove-described embodiments may be used.

In addition, other technologies of correcting chromatic aberration in anoptical pickup is disclosed by Japanese laid-open patent applicationsNos. 2000-9047, 6-14135, 62-36621, 9-138344, etc., and these well-knownmethods may be appropriately applied. Similarly, other sphericalaberration correcting devices are disclosed by Japanese laid-open patentapplications Nos. 2000-13160, 10-20263, etc., and such a sphericalaberration correcting device may be appropriately utilized in thisoptical information processing device.

In each embodiment described above, generally, the optical recordingmedium applied is of a disk. The incident side substrate has thestandard thickness of 0.1 mm, and the optical system of the opticalpickup in an infinite system is designed based on this standard value.The object lens for the optical pickup is designed as one part of thisoptical system. Generally, the incident side substrate thickness in theoptical recording medium actually used possibly has an error from theabove-mentioned standard value.

Moreover, the above-mentioned conditions (9) through (12), andconditions (21) through (24) are effective on a range up to the order ofNA=9.5 and, for a practical use, up to around NA=1.0.

The above-mentioned conditions (1) through (24) are conditions for theobject lens for the optical pickup to archive the numerical aperture ofthe predetermined range, and desired performance. The meaning ofcondition (1) is the same as the meaning of conditions (5), (9), (13),(17), and (21), the meaning of condition (2) is the same as the meaningof conditions (6), (10), (14), (18), and (22), and the meaning ofcondition (3) is the same as the conditions (7), (11), (15), (19) and(23), and the meaning of condition (4) is the same as the meaning ofconditions (8), (12), (16), (20), and (24).

The object lens for the optical pickup of an infinite system is apositive lens which makes the parallel beam incident from the lightsource side condense. In each embodiment described above, either aconvex lens or a meniscus lens may be applied as the object lens, as ithas both sides each of aspherical surface. In the case of a both-sideconvex lens, in terms of aberration correction, it is preferable todispose the surface having the small curvature radius on the lightsource side. In case of meniscus lens, the convex surface may bepreferably made to face the light source side.

On the operating wavelength of 650±20 nm or the operating wavelength of407±10 nm, the allowable maximum wavefront aberration is assumed as0.01λ, where λ stands for the wavelength, in formation of a light spothaving a desired diameter on the recording surface through the incidentside substrate having the thickness of 0.01 mm.

When the object lens is of the meniscus lens having its convex surfaceface to the light source side, it is necessary that the above-mentionedconditional formulas (1), (2), (5), (6), (9), (10), (13), (14), (17),(18), (21), and (22) hold. Otherwise, it becomes not possible to archivethe desired numeral aperture, and also to have the wavefront aberrationfall within 0.01λ.

When the object lens is of the both-side convex lens having the convexsurface with smaller curvature radius face the light source side, theabove-mentioned conditional formulas (1), (2), (5), (6), (9), (10),(13), (14), (17) (18), (21), and (22), and, also, conditional formulas(3), (4), (7), (8), (11), (12), (15), (16), (19), (20), (23) and (24)should preferably hold. Also, these conditional formulas (3), (4), . . ., (23) and (24) should preferably hold in case the object lens is of ameniscus lens having the convex surface facing the light source side.

The conditions (1) and (13) are the same, and, define the paraxialcurvature radius R1, the refractive index nd of the lens material withrespect to the d-line, and the focal length f. For example, a case isassumed in which NA is 0.65≦NA<0.75. In such a case, parameters R1 andnd for the purpose of achieving NA=0.65 will now be discussed.

Supposing the light-source-side surface of the object lens is a convexto the light source side, that the paraxial curvature radius R1 becomeslarger means that the positive refraction power on this surface becomessmaller. According to the present invention, to enlarge the numericaperture of the object lens for the optical pickup is aimed. For thispurpose, it is necessary to enlarge the positive refraction power in thelens. In order to enlarge the numerical aperture NA while enlarging theparaxial curvature radius R1, it is necessary to enlarge the refractiveindex of the lens material itself. Accordingly, the refractive index ndof the lens material should be increased with increase in the paraxialcurvature radius R1 thereof.

Black dots shown in FIG. 33 plot a relation between the paraxialcurvature radius R1 and the refractive index nd of the object lens forthe optical pickup to satisfy the condition that the wavefrontaberration be not more than 0.01λ, in the both-side-convex type havingthe surface with the sharper curvature face the light source side, withthe effective diameter φ=3 mm and the numerical aperture NA=0.65. Theseblack dots lie on a straight line 14-1 as shown in the figure.Therefrom, it can be seen that the paraxial curvature radius R1, and therefractive index nd have a linear proportionality relation.

On the other hand, between the numerical aperture NA and the focallength f, the following relation holds:f=(φ/2)/NAAs φ=3 mm and NA=0.65, it is found out f=2.31 mm. Then, by using thisvalue in the focal length, the relation of the straight line 14-1 inFIG. 33 is obtained with respect to the parameter R1/f and nd asvariables. Then, the following formula is obtained:R1/f=1.3nd−1.2

In case the relation between R1, nd and f separates from this formula,even when the aspherical shape on the light-source side oroptical-recording-medium side surface, or the lens thickness/material isappropriately adjusted, the wavefront aberration of not more than 0.01λwith the numerical aperture NA 0.65 cannot be attained.

Triangle dots shown in FIG. 33 plot the relation with the numericalaperture NA=0.75 for the wavefront aberration to be not more than 0.01λ.As shown, this relation lies on a straight line 14-2. This straight line14-2 is in the same way expressed by the following formula:R1/f=1.2nd−1.1

In case the relation between R1, nd and f separates from this formula,even when the aspherical shape on the light-source-side or theoptical-recording-medium-side surface, or the lens thickness/material isAppropriately adjusted, the numeric aperture NA: 0.75 with the wavefrontaberration of not more than 0.01λ cannot be attained.

Similarly, white squire dots shown in FIG. 33 shows the same relationwith the numeric aperture NA=0.85 and the wavefront aberration of notmore than 0.01λ. This relation lies on a straight line 14-3, and can beexpressed by the following formula:R1/f=1.0nd−0.7

In case the relation between R1, nd and f separates from this formula,even when the aspherical shape on the light-source-side oroptical-recording-medium-side surface of the lens, or the lensthickness/material is adjusted, the numeric aperture NA: 0.85 with thewavefront aberration of not more than 0.01λ cannot be attained.

Therefrom, it can be seen that the straight line which expresses therelation between R1 and nd has the slope that becomes less steep as thenumerical aperture NA becomes larger.

Accordingly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ and the numeric aperture NAin such a range that0.65≦NA<0.75,the parameters R1/f and nd should satisfy the conditional formulas (1),(13) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.Similarly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ, and the numeric aperture NAin such a range that0.75≦NA<0.85,the parameters R1/f and nd should satisfy the conditional formulas (5),(17) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.

Similarly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ, and the numeric aperture NAin such a range that0.85≦NA,the parameters R1/f and nd should satisfy the conditional formulas (9),(21) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.

How to secure the working distance required in order that the objectlens for the optical pickup have improved reliability in the opticalpickup will now be discussed. In order to enlarge the working distanceWD, the back focus (back focal distance) should be enlarged. For thispurpose, the refractive index of the object lens for the optical pickupis made smaller so as to make the refraction power smaller. However,this leads to reduction in the numeric aperture. Therefore, in order tosecure necessary the working distance, with securing the necessarynumeric aperture, the numeric aperture and the refractive index are madeto balance.

FIG. 34 shows relation of the working distance WD with respect to therefractive index nd of the lens material for the respective requirednumerical aperture 0.65, 0.75 and 0.85, under the condition that thewavefront aberration is controlled within 0.01λ, the effective diameteris such that φ=3 mm, with the both-side-convex object lens having thesurface with shaper curvature toward the light source side. In FIG. 33,the curve 15-1 shows the relation for NA=0.65, the curve 15-2 shows therelation for NA=0.75, and the curve 15-3 shows the relation for NA=0.85.The curve 15-1 can be expressed by the following formula, where theparameters WD/f and nd are regarded as variables:WD/f=0.39nd−0.04

In case the relation between WD, nd and f separates from this formula,even when the aspherical shape on the light-source-side oroptical-recording-medium side surface of the lens, or the lensthickness/material is adjusted, the required numeric aperture of 0.65with the wavefront aberration of not more than 0.01λ cannot be attained.

Similarly, the curve 15-2 can be expressed by the following formula,where the parameters WD/f and nd are regarded as variables:WD/f=0.37nd−0.14

In case the relation between WD, nd and f separates from this formula,even when the aspherical shape on the light-source-side oroptical-recording-medium side surface of the lens, or the lensthickness/material is adjusted, the required numeric aperture of 0.75with the wavefront aberration of not more than 0.01λ cannot be attained.

The curve 15-3 can be expressed by the following formula, where theparameters WD/f and nd are regarded as variables:WD/f=0.33nd−0.18

In case the relation between WD, nd and f separates from this formula,even when the aspherical shape on the light-source-side oroptical-recording-medium side surface of the lens, or the lensthickness/material is adjusted, the required numeric aperture of 0.85with the wavefront aberration of not more than 0.01λ cannot be attained.

Therefrom, it can be seen that the straight line which expresses therelation between WD and nd has the slope that becomes less steep as NAbecomes larger.

Accordingly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ, the numeric aperture NA isin such a range that0.65≦NA<0.75,the parameters R1/f and nd should satisfy the conditional formulas (2),(14) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.

Similarly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ, the numeric aperture: NA isin such a range that0.75≦NA<0.85,the parameters R1/f and nd should satisfy the conditional formulas (6),(18) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.

Similarly, on the object lens for the optical pickup having thewavefront aberration of not more than 0.01λ, the numeric aperture: NA isin such a range that0.85≦NA,the parameters R1/f and nd should satisfy the conditional formulas (10),(22) whether or not the operating wavelength is 407±10 nm, or 660±20 nm.

FIGS. 35A through 35F show the lens material with the refractive indexnd and Abbe's number νd under the condition where the above-mentionedrespective conditional formulas (1), (2), (5), (6), (9), (10), (13),(14), (17), (18), (21), and (22) are satisfied, with theboth-side-convex objective lens with the surface having the shapercurvature face the light source side, with the required respectivenumeral aperture, and the wavefront aberration of not more than 0.01λ.

FIGS. 35A, 35B and 35C show the cases of operating wavelength of 650 nm,with the numeral aperture of 0.65, 0, 75 and 0.85, respectively. FIGS.35D, 35E and 35F show the cases of operating wavelength of 407 nm, withthe numeral aperture of 0.65, 0, 75 and 0.85, respectively. In thesefigures, the lens materials having the combinations of the refractiveindex and the Abbe's number shown by the black dots are allowable. As ageneral tendency, the range permitted in the refractive index and theAbbe's number narrows as the numerical aperture NA increases. Thistendency is so remarkable in the operating wavelength 407 nm.

The conditional formulas (3), (4), (15), and (16) specify the tolerancelevel of the refractive index and the Abbe's number according to FIGS.35A and 35D. The conditional formulas (7), (8), (19) and (20) specifythe tolerance level of the refractive index and the Abbe's numberaccording to FIGS. 35B and 35E. The conditional formulas (11), (12),(23), and (24) specify the tolerance level of the refractive index andthe Abbe's number according to FIGS. 35C and 35F.

In case the conditional formulas (4), (8), (12), (16), (20) and (24) donot hold in case the object lens for the optical pickup is of aboth-side-convex type having the surface of sharper curvature face thelight-source side, the refractive index of the object lens is too small.Accordingly, in order to achieve the desired NA, the curvature of thelens surface on the light source side in particular should be sharpened.As a result, it will become difficult to form the object lens surface ata high precision, and the cost of the object lens will become higher.

In case the conditional formulas (3), (7), (11), (15), (19), and (23) donot hold, chromatic aberration due to change of the wavelength of thelight source becomes increased too much. These conditions concerning theAbbe's number and refractive index should be preferably satisfiedespecially in a case where the object lens for the optical pickup is ofthe both-side-convex type and having the surface of shaper curvatureface the light source side.

As described in the description of the embodiments above, satisfactoryperformance having the wavefront aberration of not more than 0.01λ canbe achieved also on the object lens for the optical pickup of a meniscustype having the convex surface face the light source side, by satisfyingthe conditions (1), (2), (5), (6), (9), (10), (13), (14), (17), (18),(21), and (22) according to the particular numeric aperture NA.

In the case of the meniscus object lens, since the surface on the sideof the optical recording medium is a concave surface, the refractionpower resulting from the lens surface is smaller in comparison to thecase of the both-side-convex object lens. Accordingly, it is preferableto select a lens material having high refractive index so as tocompensate this. Moreover, since the direction of chromatic aberrationoccurring is different between the surface on the light source side andthe surface on the optical recording medium side, a lens material havinga large dispersion and a small Abbe's number can be used. That is, inthe object lens for optical pickup of meniscus type, the material ofboth-high refractive index and low Abbe's number can be used incomparison to the case of applying the both-side-convex time type.

However, also in case of the meniscus object lens for the optical pickuphaving the convex surface face the light source side, by satisfying theabove-mentioned conditions (3), (7), (11), (15), (19), and (23), therequirements concerning the lens shape such as lens surface shape areeased.

Thus, by configuring an object lens for an optical pickup satisfying theabove-mentioned respective conditions, it is possible to realize theobject lens for the optical pickup with which it has the numericaperture falling within the required range, and the wavefront aberrationof not more than 0.01λ.

Other embodiments of the present invention will now be described withreference to drawings.

Same as the above-described embodiments of the present invention, as aform of an optical recording medium, a disk-shaped one is used. Further,the incident side substrate of the optical recording medium has athickness of a standard value of 0.1 mm. Based on this standard value,an optical system of an optical pickup is designed and theabove-mentioned incident side substrate thickness may possibly have anerror from the above-mentioned standard value in the optical recordingmedium actually used.

First, conditional formulas I, II, III, IV, and V will now be described.In these formulas, the refractive-index of material with respect to thed-line is referred to as nd, the Abbe's number of the material withrespect to the d-line is referred to as νd, the lens central thicknessis referred to as t, the working distance is referred to as WD, thefocal length is referred to as f, the paraxial curvature radius on thesurface facing the light source side is referred to as R1. Theconditional formulas are shown below:νd≦65  Conditional formula I:1.55≦nd  Conditional formula II:1.0nd−1.0≦R1/f≦1.0nd−0.8  Conditional formula III:1.2nd−0.75≦t/f≦1.2nd−0.5  Conditional formula IV:−0.35nd+0.77≦WD/f≦−0.35nd+0.85  Conditional formula V:These conditional formulas I through V define conditions for the objectlens for the optical pickup realizing a desired performance.

The object lens for the optical pickup used as the infinite system lensis a positive lens which makes a parallel beam incoming from the lightsource side condense, and, a both-side-convex lens or a meniscus lensmay be applied thereto. As mentioned above, in the object lens for theoptical pickup, the both sides thereof are of aspherical surfaces with asingle lens configuration. However, since the light-source-side surfaceof the both-side-convex lens can be made less sharp in curvature, theboth-side-convex lens is preferable in the viewpoint of manufactureimplementability.

In the embodiments of the present invention which will be describedlater, the maximum value of wavefront aberration is made to fall within0.04λ in order to form a satisfactory light spot with a desired diameteron a recording surface of an optical recording medium with the lightsource of predetermined wavelength, and the incident side substrate ofthe optical recording medium having a predetermined thickness. Thiswavefront aberration of 0.04λ includes a wavefront degradation occurringdue to manufacture error, such as a curvature radius deviation on thefirst/second surfaces of the lens, a thickness deviation of the lens, adeviation of the aspherical surface shape, a shift of each surface ofthe lens, a tilt of each surface of the lens, and so forth. Therefore, amaximum permissible value in the amount of wavefront degradationoccurring due to these manufacture errors is determined as the order of0.015λ.

FIG. 36 expresses the lens material permitted in order to realize thewavefront aberration not more than 0.04λ with a relation between therefractive index nd and Abbe's number νd. In case the object lens forthe optical pickup is of a both-side-convex type with the surface havingthe shaper curvature face the light source side, but the above-mentionedcondition II, i.e., 1.55≦nd, cannot be satisfied, the refractive indexof the object lens becomes too small. Accordingly, in order to achievethe desired NA, it is necessary to sharpen the curvature on the lenssurface facing the light source side. In such a case, it becomesdifficult to form the object lens surfaces at high accuracy, and, thus,the cost of the object lens increases.

Moreover, when the condition I, i.e., νd≦65, concerning the Abbe'snumber νd cannot be satisfied, chromatic aberration occurring due tovariation in the wavelength of the light source becomes large too much.

These conditions concerning the Abbe's number and refractive index arepreferably satisfied especially in the case where the object lens forthe optical pickup is of both-side-convex type having the surface withshaper curvature face the light source side.

Furthermore, to control the wavefront aberration within 0.04λ withsecuring the necessary numerical aperture cannot be achieved unless theabove-mentioned conditions III and IV are satisfied, in the case wherethe object lens for the optical pickup is of the both-side-convex typehaving the surface of shaper curvature face the light source side.

The paraxial curvature radius R1, the lens central thickness t, and therefractive index nd on the above-mentioned conditions III and IV willnow be discussed. Supposing the surface on the side of the light sourceof the object lens for the optical pickup is convex toward the lightsource side, that the paraxial curvature radius R1 becomes large meansdecrease in the positive refraction power on this surface. On the otherhand, in order to enlarge NA of the object lens for the optical pickup,it is necessary to enlarge the positive refraction power on this lenssurface. Therefore, in order to enlarge NA at the same time to enlargethe paraxial curvature radius R1, it is necessary to enlarge therefractive index of the lens material as mentioned above. Accordingly,the relation is to hold in which the refractive-index nd of the lensmaterial is made to increase with increase of the paraxial curvatureradius R1.

On the other hand, when the central thickness t of the lens becomeslarger, an area by which the light passes through the surface on theside of the optical recording medium becomes smaller. As mentionedabove, in order to enlarge NA of the object lens for the optical pickup,it is necessary to enlarge the positive refraction power on this lenssurface. Accordingly, in order to enlarge NA at the same time toincrease the lens central thickness t, the relation should hold in whichthe refractive index nd of the lens material is made to increase withthe increase of the central thickness t of the lens.

Black dots shown in FIG. 37A plot the relation which the paraxialcurvature radius R1 and refractive index nd should satisfy under thecondition where the wavefront aberration of not more than 0.04λ issecured, and, the focal length f of the object lens for the opticalpickup of both-side-convex type having the shaper curvature surface facethe light source side is set as 1.765 mm, and NA=0.85, as example.Similarly, white triangles of FIG. 37A plot another example in whichf=2.235 mm and NA=0.85. That is, the required relation is included in azone sandwiched by curves (actually, straight lines) 2 a-1 and 2 a-2.Since the refractive index of the lens material depends also on theAbbe's number νd in addition to the refractive-index nd of d-line, therelation between R1 and nd cannot be determined uniquely. However, it ispossible to achieve the wavefront aberration not more than 0.04λ bysatisfying the condition III concerning R1 and nd according to the zonebetween the straight lines 2 a-1 and 2 a-2, and, also, by satisfying thecondition I concerning νd.

Similarly, black dots shown in FIG. 37B plot the relation which thecentral lens thickness t and refractive index nd should satisfy underthe condition where the wavefront aberration of not more than 0.04λ issecured, and, the focal length f of the object lens for the opticalpickup of both-side-convex type having the shaper curvature surface facethe light source side is set as 1.765 mm, and NA=0.85, as example.Similarly, white triangles of FIG. 37B plot another example in whichf=2.235 mm and NA=0.85. That is, the required relation is included in azone sandwiched by curves (actually, straight lines) 2 b-1 and 2 b-2.Since the refractive index of the lens material depends also on theAbbe's number νd in addition to the refractive-index nd of d-line, therelation between t and nd cannot be determined uniquely. However, it ispossible to achieve the wavefront aberration not more than 0.04λ bysatisfying the condition IV concerning t and nd according to the zonebetween the straight lines 2 b-1 and 2 b-2, and, also, by satisfying thecondition I concerning νd.

Next, as mentioned above, the working distance WD should be secured inorder that the object lens for the optical pickup be improved in thereliability.

As mentioned above, enlargement in the working distance WD is achievableby the increase in the back focus. However, for this purpose, therefractive index in the object lens for the optical pickup should bereduced. However, reduction in the refractive index of the object lensleads to reduction in NA. Therefore, in order to secure the necessaryworking distance WD, while securing the necessary NA, NA and nd are madeto balance.

Black dots in FIG. 37C plot the relation between the working distance WDand the refractive index nd of the lens material under the condition ofachievement of the wavefront aberration of not more than 0.04λ on theobject lens for the optical pickup having the focal length f=1.765 andNA=0.85 of the both-side-convex type having the shaper curvature sideface the light source side. Similarly, white triangles of FIG. 37C plotthe relation in another example where f=0.2.235, and NA=0.85. That is,the required relations are included in the zone defined between thestraight lines 2 c-1 and 2 c-2. Since the refractive index of the lensmaterial depends also on the Abbe's number νd in addition to therefractive-index nd of d-line, the relation between WD and nd cannot bedetermined uniquely. However, it is possible to achieve the wavefrontaberration not more than 0.04λ by satisfying the condition V concerningWD and nd according to the zone between the straight lines 2 c-1 and 2c-2, and, also, by satisfying the condition I concerning νd. Inaddition, the effective diameter on the light-source-side surface of theobject lens should fall within a range between 3 mm and 4 mm in theviewpoints of the working distance and object lens weight.

If the relations separate from the above-mentioned conditions III, IVand V, even when aspherical shapes on the lens surfaces on the lightsource side and optical recording medium side are adjusted, it is notpossible to achieve the wavefront aberration of not more than 0.04λ withNA: 0.85.

Thus, it is possible by satisfying the above-mentioned conditions I andII to realize the object lens for the optical pickup having thenumerical aperture in the necessary range, and the wavefront aberrationof not more than 0.04λ. Also, the implementability on manufacture canimprove further on the object lens for the optical pickup by satisfyingthe above-mentioned conditions III, IV and V.

Object lenses for optical pickups according to embodiments 13 and 14 ofthe present invention will now be described. In the configurations shownin FIG. 38A and FIG. 39A, in order to avoid complication, the samereference numerals are given to parts/members having substantially thesame functions. Specifically, as shown in the figures, a beam emittedfrom a light source is incident on an object lens 2 after passingthrough an aperture 1, and then, is incident on a recording surface RSthrough an incident side substrate 3 (with the thickness of 0.1 mm) bothof an optical recording medium.

The laser beam from the light source side (not shown, and located in theleft-hand side of the figures) passes through an opening (with thediameter φ=3 mm or 4 mm) of the wavelength selecting aperture 1 as aparallel beam, and, is incident on the object lens 2 for the opticalpickup. Then, the incident beam is made a condensing beam by means ofthis object lens 2, passes though the incident side substrate 3 of theoptical recording medium, and then, forms a light spot on the recordingsurface RS (i.e., the right-hand end surface of the incident sidesubstrate 3).

The aspherical surfaces on the lens surfaces of the object lens 2 areexpressed by the following well-known aspherical surface formula withcoordinates X along the optical axis direction, coordinates Y along adirection perpendicular to the optical axis, a paraxial curvature radiusR, a cone constant K, and high order coefficients A, B, C, D, E, F, . .. :X=(Y ² /R)/[1+√{1−(1+K)Y/R ² }+AY ⁴ +BY ⁶ +CY ⁸ +DY ¹⁰ +EY ¹² +FY ¹⁴ +GY¹⁶ +HY ¹⁸ +JY ²⁰+ . . .where R, K, A, B, C, D . . . are given, and thereby, the shape isdefined.

First, on the object lens for the optical pickup in the embodiment 13 ofthe present invention, the applied operating wavelength: 407 nm, NA:0.85, f: 1.765 mm, nd: 1.69350, and νd: 53.2. FIG. 40 shows otherspecific data thereof.

In FIG. 40, “OBJ” means an object point (a semiconductor laser as thelight source). The object lens 2 for the optical pickup is of aninfinite system, and “INFINITY” as the curvature radius RDY andthickness THI in the table of FIG. 40 means that the light sourcesubstantially located at infinity (i.e., in the infinite system asmentioned above). Moreover, in the table, “STO” stands for the surfaceon the wavelength selection aperture 1, and the curvature radius RDYthereof is set “INFINITY”, and the thickness THI thereof is set “0” onthe design. In addition, unless any other special notice, the unit ofthe dimension of length is “mm.”

“S1” means the light-source-side surface of the object lens for theoptical pickup, while “S2” means the optical-recording-medium-sidesurface of the same. The thickness of the object lens 2 in theembodiment 13 is 2.381463 mm, and “0.425496 mm” in thickness indicatedon the right-hand side of the curvature radius of the field on S2 shows“working distance WD”, in the table.

“S3” stands for the light-source-side surface of the incident sidesubstrate 3 of the optical recording medium, and “S4” stands for therecording surface RS of the same. The separation between these surfacesS3 and S4, i.e., the incident side substrate thickness, is 0.1 mm, nd:1.516330, and νd: 64.1 on the same. “EPD (entrance pupil diameter)” inthe table expresses the diameter (3 mm) of an opening of the wavelengthselection aperture 1, and “WL: wavelength” expresses the operatingwavelength (407 nm).

In addition, in the indication of the above-mentioned aspherical surfacecoefficients in the table, for example, the indication of “D:0.305477E-03” means “D=0.305477×10⁻³.” The same manner is applied toevery table.

The arrangement of the wavelength selection aperture 1, the object lens2 for the optical pickup, and the incident side substrate 3 in theembodiment 13 is shown in FIG. 38A. The astigmatism of the object lens 2for the optical pickup and the spherical aberration of the same (thescale on the vertical axis stands for the values obtained according tonormalization of the entrance pupil radius to 1) are shown in FIG. 38Band FIG. 38C, respectively. As can be seen therefrom, both theaberrations are satisfactorily corrected. In fact, the wavefrontaberration of the design median is 0.0022λ on the axis.

Furthermore, the amount of aberration increase when the centralthickness deviation of the lens occurs is shown in FIG. 38D. In FIG.38D, the dashed line stands for the amount of aberration increase on theoperating wavelength: 650 nm, NA: 0.75, f: 2.00 mm, nd: 1.69330 and νd:53.17, caused by the central thickness deviation in a conventionalobject lens, and the solid line shows the same on the embodiment 13according to the present invention. Compared with the conventionalobject lens, even in case there is a thickness deviation about ±1micrometer, the wavefront degradation is below 0.006λ, and is in therange which can sufficiently be manufactured according to the presentinvention.

As mentioned above, the object lens according to the thirteenthembodiment has the paraxial curvature radius: R1=1.37595 mm on the sideof light source, f=1.765 mm, nd=1.69350, νd=53.2, and WD=0.425496 mm,and, as a result, R1, t, WD, f, nd and νd are within the ranges whichsatisfy the above mentioned conditions I through V, respectively.

Next, the focal length f in the object lens for the optical pickupaccording to the embodiment 14 of the present invention differs fromthat of the above-described embodiment 13, and, the embodiment 14 hasthe following specification: NA: 0.85, f=2.353 mm, nd=1.69350, andνd=53.2. FIG. 41 shows other specification.

The arrangement of the wavelength selection aperture 1, the object lens2 for the optical pickup, and the incident side substrate 3 is shown inFIG. 39A. The astigmatism of the object lens 2 for the optical pickup inthe embodiment 14 and the spherical aberration thereof (the scale on thevertical axis stands for the values obtained according to normalizationof the incidence pupil radius to 1) are shown in FIGS. 39B and 39C,respectively. As can be seen therefrom, both the aberrations are wellcorrected. In fact, the wavefront aberration of the design median is0.0043λ on the axis.

As mentioned above, since the object lens in the embodiment 14 has thespecification, i.e., R1=1.8331 mm, f=2.353 mm, nd=1.69350, νd=53.2, andWD=0.588459 mm, R1, t, WD, f, nd and νd fall within the respectiveranges which satisfy the above-mentioned conditions I through V as wellas in the above-described embodiment 13.

Next, conditions VI and VII to be satisfied for achieving desiredperformance also on a conventional optical recording medium such as DVD,CD, or the like by using the object lens for the optical pickupaccording to the present invention having the specification, i.e., theoperating wavelength: 407±10 nm, NA: 0.85±0.05, for an optical recordingmedium having the incident side substrate with the thickness of 0.1 mm,will now be described:−0.42nd+0.82≦WD/f≦−0.42nd+0.95  Condition VI:−0.35nd+0.64≦WD/f≦−0.35nd+0.72  Condition VII:The meaning of the condition VI is the same as the meaning of thecondition VII.

In order to focus a beam on a DVD-type optical recording medium, theobject lens applied should have the capability of focusing with anoperating wavelength: 660±10 nm and NA: 0.65±0.05 onto the opticalrecording medium having the incident side substrate with the thicknessof 0.6 mm.

Similarly, in order to focus on a CD-type optical recording medium, theobject lens applied should have the capability of focusing with anoperating wavelength: 780±10 nm and NA 0.50±0.05 onto the recordingmedium with the incident side substrate of the thickness of 1.2 mm.

In case the object lens according to the present invention is also usedon the condition of the operating wavelength and substrate thicknessaccording to the DVD or CD, the spherical aberration may occur due todifference in the substrate thickness (0.1 mm, 0.6 mm, 1.2 mm) and thedifference in wavelength (407 nm, 660 nm, 780 nm). In order to controlthis spherical aberration, when performingrecording/reproduction/deletion of information on a DVD or a CD, theincident beam onto the object lens should be of a divergent type. Thatis, when performing recording/reproducing/deleting of information on aDVD or a CD, the object lens is used as a finite-system object lens.Some spherical aberration remains slightly even when the incident beamonto the object lens is in a divergent type. This can be effectivelyreduced by inserting a coupling lens having a surface with a shapercurvature face the object lens side between the light source and theobject lens. Moreover, as to the difference in NA (0.65, 0.85 and 0.50),the problem can be solved by using a device which can control thenumerical aperture according to the particular operating wavelength.

Then, the object lens for the optical pickup which satisfies theabove-mentioned conditions I through V with the operating wavelength:407±10 nm and NA: 085±0.05 for the incident side substrate thickness:0.1 mm is used as an object lens for an optical pickup (for DVD) whichcan focus onto an optical recording medium under the condition of theoperating wavelength: 660±10 nm and NA: 0.65±0.05, for the incident sidesubstrate thickness: 0.6 mm.

Then, under the condition where the spherical aberration occurring dueto the difference in the substrate thickness and operating wavelength iscontrolled to the minimum, relation between the working distance WD andrefractive index nd has been studied. As a result, on examples in thefocal length: f=1.8 through 1.9 mm, black dots shown in FIG. 42A areplotted. Similarly, for other examples in f=2.4 through 2.5 mm and NA:0.85, white triangles are plotted in FIG. 42A. That is, the relationsare included within a zone defined by the straight line 5 a-1 and thestraight line 5 a-2. Since the refractive index depends not only on therefractive nd on the d-line but also on the Abbe's number νd, therelation between WD and nd cannot be determined uniquely. However, it ispossible to control the spherical aberration occurring due to thedifference in substrate thickness and operating wavelength within theminimum as a result of establishment of a configuration such as tosatisfy the condition VI of WD and nd determined as the zone between thestraight lines 5 a-1 and 5 a-2, and, also, to satisfy the condition Iconcerning νd.

Similarly, the object lens for the optical pickup which satisfies theabove-mentioned conditions I through V with the operating wavelength:407±10 nm and NA: 085±0.05 for the incident side substrate thickness:0.1 mm is used as an object lens for an optical pickup (for CD) whichthus can focus onto an optical recording medium under the condition ofthe operating wavelength: 780±10 nm and NA: 0.50±0.05, for the incidentside substrate thickness: 0.6 mm. Then, under the condition where thespherical aberration occurring due to the difference in the substratethickness and operating wavelength is controlled to the minimum,relation between the working distance WD and refractive index nd hasbeen studied. As a result, on examples in the focal length: f=1.8through 1.9 mm, black dots shown in FIG. 42B are plotted. Similarly, forother examples in f=2.4 through 2.5 mm and NA: 0.85, white triangles areplotted in FIG. 42B. That is, the relations are included within a zonedefined by the straight line 5 b-1 and the straight line 5 b-2. Sincethe refractive index depends not only on the refractive nd on the d linebut also on the Abbe's number νd, the relation between WD and nd cannotbe determined uniquely. However, it is possible to control the sphericalaberration occurring due to the difference in substrate thickness andoperating wavelength within the minimum as a result of establishing aconfiguration such as to satisfy the condition VII of WD and nddetermined as the zone between the straight lines 5 b-1 and 5 b-2, and,also, to satisfy the condition I concerning νd.

Thus, by satisfying the above-mentioned condition VI or VII, it ispossible to realize an optical pickup for recording/reproducing/deleinginformation on DVD or CD of conventional standard type by using anoptical pickup in infinite system prepared for the operating wavelengthof 407±10 nm and NA: 0.85±0.05, and for the incident side substrate withthe thickness of 0.1 mm.

As embodiments 15 and 16 of the present invention, object lenses foroptical pickups of so-called compatibility type which can performrecording/reproduction/deletion on both a large-capacity opticalrecording medium for the operating wavelength: 407 nm, and NA: 0.85, andconventional optical recording medium, such as a DVD or CD will now bedescribed with reference to FIGS. 43A and 44A. Also in each of thesefigures, similar to the embodiments 13 and 14 described above withreference to FIGS. 38A and 39A, a beam coming from a light source passesthrough a wavelength selection aperture 1 and an object lens 2, andthen, is incident on a recording surface RS through an incident sidesubstrate 3 both of an optical recording medium. Furthermore, a couplinglens 5 is inserted having a concave surface. The incident side substrate3 has the thickness of 0.6 mm on DVD and of 1.2 mm on CD.

Through the coupling lens 5, the light beam emitted from the lightsource 4 passes through the opening (diameter of the opening: φ=3.24570mm) of the wavelength selection aperture 1 as a divergent beam, isincident onto the object lens 2, which then transforms the incident beaminto a converging beam. The converting beam is then incident on therecording surface RS through the incident side substrate 3 of theoptical recording medium, and, thus, forms a light spot on the recordingsurface RS.

The aspherical surface on each of the lens surfaces are expressed by thefollowing well-known aspherical surface formula with coordinates X alongthe optical axis direction, coordinates Y along a directionperpendicular to the optical axis, a paraxial curvature radius R, a coneconstant K, high order coefficients A, B, C, D, E, F, . . . .X=(Y ² /R)/[1+√{1−(1+K)Y/R ² }+AY ⁴ +BY ⁶ +CY ⁸ +DY ¹⁰ +EY ¹² +FY ¹⁴ +GY¹⁶ +HY ¹⁸ +JY ²⁰+ . . . ,where R, K, A, B, C, D, . . . , are given, and thereby, the shape isdefined.

The embodiment 15 corresponds to a case where the object lens 2according to the above-described embodiment 13 is applied as an objectlens for dealing with DVD. First, on the object lens for the opticalpickup, the applied wavelength: 660 nm, NA: 0.65, f: 2.4230 mm, nd:1.51680, and νd: 64.2. FIG. 45 shows other specific data.

In FIG. 45, “OBJ” means an object point (a semiconductor laser as thelight source). The object lens 2 for the optical pickup is used as afinite system in the case of dealing with DVD. The curvature radius isreferred to as RDY and the thickness is referred to as THI also in thetable of FIG. 45. Moreover, in the table, “STO” stands for the surfaceon the wavelength selection aperture 1, and the curvature radius RDYthereof is set as “INFINITY”, and the thickness THI thereof is set as“0” on the design. In addition, unless any other special notice, theunit of the dimension of length is “mm.”

“S2” means the light-source-side surface of the coupling lens 5, while“S3” means the optical-recording-medium-side surface of the same. “S5”means the light-source-side surface of the object lens 2 for the opticalpickup, while “S6” means the optical-recording-medium-side surface ofthe same. The thickness of the object lens 2 in the embodiment 15 is3.174078 mm, and “0.501457 mm” in thickness indicated on the right-handside of the curvature radius of the field on S6 shows “working distanceWD.”

“S7” stands for the light-source-side surface of the incident sidesubstrate 3 of the optical recording medium, and “S8” stands for therecording surface of the same. The separation between these surfaces S7and S8, i.e., the incident side substrate thickness, is 0.6 mm, nd:1.516330, and νd: 64.1 on the same. “EPD (entrance pupil diameter)” inthe table expresses the diameter (3.24570 mm) of an opening of thewavelength selection aperture 1, and “WL: wavelength” expresses theoperating wavelength (660 nm).

The arrangement of the wavelength selection aperture 1, the object lens2 for the optical pickup, the incident side substrate 3, the couplinglens 5, and the light source 4 is shown in FIG. 43A. FIG. 43B showsrelations between the optical system configuration and wavefrontaberration in case the object lens 2 according to the above-describedembodiment 13 is used for focusing in the condition of the operatingwavelength: 660 nm, substrate thickness: 0.6 mm, and NA: 0.65.Specifically, the respective wavefront aberrations occurring in a case(1) of incidence in an infinite system, in a case (2) of incidence in afinite system, and in a case (3) of incidence in a finite system byusing the coupling lens (corresponding to the embodiment 15 shown inFIG. 43A) are shown in the figure. As can bee seen therefrom, accordingto the embodiment 15, the aberration is very well corrected.

As mentioned above, since the object lens 2 according to the embodiment15 has the specification, i.e., nd: 1.69350, νd: 53.2, f: 2.4299 mm, andWD: 0.501457 mm, WD, f, nd and νd fall within the respective rangeswhich satisfy the above mentioned condition I, condition II, andcondition VI.

As the embodiment 16 of the present invention, the object lens for theoptical pickup has the specification of the operating wavelength: 780 nmfor CD, and other specification is shown in FIG. 46 in the same manneras in FIG. 45 for the embodiment 15.

FIG. 44A shows the arrangement of the wavelength selection aperture 1,the object lens 2 for the optical pickup, the incident side substrate 3,the coupling lens 5, and the light source 4 according to the embodiment16. FIG. 44B shows relations between the optical system configurationand wavefront aberration in case the object lens 2 according to theabove-described embodiment 13 is used for focusing in the condition ofthe operating wavelength: 780 nm, substrate thickness: 1.2 mm, and NA:0.50. Specifically, the respective wavefront aberrations occurring in acase (1) of incidence in an infinite system, in a case (2) of incidencein a finite system, and in a case (3) of incidence in a finite system byusing the coupling lens (corresponding to the embodiment 16 shown inFIG. 44A) are shown in the figure. As can bee seen therefrom, accordingto the embodiment 16, the aberration is very well corrected.

As mentioned above, since the object lens 2 according to the embodiment16 has the specification, i.e., nd: 1.69350, νd: 53.2, f: 2.4445 mm, andWD: 0.236004 mm, WD, f, nd and νd fall within the respective rangeswhich satisfy the above mentioned condition I, condition II, andcondition VII.

Furthermore, the embodiments 15 and 16 can be embodied at the same time,i.e., in a common single optical pickup.

FIG. 47 shows a block diagram showing an outline configuration of anoptical pickup according to an embodiment 17 of the present invention.In the embodiment 17, the object lens according to the embodiment(s) 13and/or 14 described above is used.

As shown in the figure, this optical pickup includes a semiconductorlaser 101 and collimator lens 102, a polarization beam splitter 103, adeflection prism 104, a ¼-wave plate 105, an object lens 106, adetection lens 108, and a light-receiving device 109.

A laser beam emitted from the semiconductor laser 101 is transformedinto a substantially parallel beam by the collimator lens 102, passesthrough the polarization beam splitter 103, is bent its course by 90degrees by the deflection prism 104, is transformed into a convergentbeam through the object lens 106, is incident onto the optical recordingmedium 107 (incident side substrate thickness: 0.1 mm), passes throughthe incident side substrate, and forms a light spot on the recordingsurface of the optical recording medium.

The ¼-wave board 105 is arranged in front of the object lens 106, andthereby, linear polarization originating from the light source istransformed into circular polarization. A beam reflected by the opticalrecording medium 107 goes reversely as a return beam, and is incident onthe polarization beam splitter 103 through the object lens 106, the¼-wave plate 105, and the deflection prism 104.

The return beam incident on the ¼-wave plate has circular polarizationdifferent from the forward passing occasion, and is transformedtherewith into a beam having a linear polarization perpendicular to thepolarization direction at the time of forward passing occasion. Afterthat, the beam is reflected by the polarization beam splitter 103. Thereturn beam reflected by the polarization beam splitter 103 is incidenton the light-receiving device 109 through the detection lens 108.

The light-receiving device 109 has a light-receiving surface suitablydivided according to a relevant servo signal creation method applied.Based on the photoelectric output from each light-receiving divisionelement, a tracking signal and a focusing signal are generated, and areproduction signal is generated with these signals at an occasion ofinformation reproduction. Moreover, these signals are output towards acontrol circuit which is not shown.

FIG. 48A is a block diagram showing an outline configuration of anoptical pickup according to an embodiment 18 of the present invention.The same reference numerals are given to parts/components correspondingto those or having equivalent functions to those shown in FIG. 47, andduplicated description will be omitted.

The object lens described above according to the embodiment(s) 15 and/or16 is used in this embodiment 18. The optical pickup shown in FIG. 48Acan deal with not only a large-capacity optical recording medium havingthe specification of the operating wavelength: 407 nm, and NA: 0.85, butalso a DVD-type optical recording medium of the operating wavelength:660 nm and NA: 0.65.

A case of dealing with the larger-capacity optical recording medium ofthe operating wavelength: 407 nm and NA: 0.85 will now be describedfirst. A semiconductor laser 101 with the wavelength of 407 nm as alight source emits a divergent beam with a linear polarization whichpasses through a collimator lens 102 and is then transformed into anapproximately parallel beam. After that, the beam passes through apolarization beam splitter 103 and a dichroic prism 203, then, afterthat, the beam course is deflected 90 degrees by the deflection prism104, and, the beam is transformed into a beam of circular polarizationby a ¼-wave plate 105. After that, the beam passes through a wavelengthselection aperture 204, and then, is incident onto an object lens 106,and it is condensed so as to form a minute spot on an optical recordingmedium 107. Information recording, reproduction, or deletion isperformed with this spot.

A beam reflected by the optical recording medium 107 passes through theobject lens 106 and the ¼-wave plate 105, it thus has a circularpolarization different from the forward passing case, and, then, istransformed again into an approximately parallel beam. After that, thebeam is reflected by the polarization beam splitter 103, is transformedinto a converging beam by a detection lens 108, and then reaches alight-receiving device 109. An information signal and a servo signal aredetected by means of the light-receiving device 109.

Next, by using the same system shown in FIG. 48A, a case of dealing witha DVD-type optical recording medium with the operating wavelength: 660nm and NA: 0.65 will now be described. In recent years, generally, ahologram unit has been used in an optical pickup for DVD in whichlight-emission/reception devices are installed into one can, and, byusing the hologram unit, a beam is separated.

As shown in FIG. 48C, such a hologram unit 201 includes a chip ofsemiconductor laser 201 a, a hologram device 201 b, and alight-receiving device 201 c, in an integrated configuration. Adivergent beam with the wavelength of 660 nm emitted from thesemiconductor laser 201 a of this hologram unit 201 passes through thehologram device 201 b. Then, as shown in FIG. 48A, the beam undergoescoupling by means of the coupling lens 202. Then, it is reflected bymeans of the dichroic prism 203 into the polarization prism 104, whichdeflects the beam course 90 degrees. After that, the ¼-wave platetransforms the beam into a beam of circular polarization, which thenpasses through the wavelength selection aperture 204, and is incident onthe optical recording medium 107 through the object lens 106. Then, itis condensed so as to form a minute spot thereon. Informationreproduction/recording/deletion is performed by this spot onto theoptical recording medium 107.

In particular, the wavelength selection aperture 204 controls thepassing beam into NA: 0.65 on a light with the wavelength: 660 nm. Thatis, as shown in FIG. 48B, the wavelength selection aperture 204 acts asan opening control device having a concentric circular shape. Then, thisdevice does not control a light with the wavelength: 407 nm, butcontrols a light with the wavelength: 660 nm light so as to pass it onlypartially by a central part thereof for achieving NA: 0.65.

A beam reflected by the optical recording medium 107 is deflected by thedeflection prism 104, is reflected by the dichroic prism 203, and istransformed into a convergent beam by means of the coupling lens 202.After that, it is diffracted by the hologram device 201 b shown in FIG.48C into the light-receiving device 201 c contained in a same cancontaining the semiconductor laser 201 a. The hologram device 201 bincludes a detection hologram 201 d which is detected by thelight-receiving device 201 c. Thus, an information signal and a servosignal are detected by means of the light-receiving device 201 c.

FIG. 49A is a block diagram showing an outline configuration of anoptical pickup in an embodiment 19 of the present invention. Thisoptical pickup according to the embodiment 19 can deal not only with alarge-capacity optical recording medium with the operating wavelength:407 nm and NA: 0.85, but also a DVD-type optical recording medium of theoperating wavelength: 660 nm and NA: 0.65, and also, a CD-type opticalrecording medium of the operation wavelength off 780 nm and NA: 0.50.

Different points from the above-described embodiment 17 will now bedescribed. This pickup has two chips of semiconductor lasers 201 a and301 a different in their wavelengths for DVD and CD, respectively.Furthermore, this pickup has two light-receiving devices, i.e.,light-receiving devices 201 c and 301 c for receiving light reflected bythe respective different optical recording media, i.e., DVD and CD.Further, a hologram unit 301 includes a hologram device 301 b forfocusing light reflected by the DVD and CD onto these twolight-receiving devices 201 c and 301 c, respectively. Furthermore, awavelength selection aperture 304 shown in FIG. 49B, which controlstransmission light of the wavelengths of 660 nm and 780 nm so as toachieve NA of 0.65 and 0.50 in case of dealing with DVD and CD,respectively. The beam passing courses and so forth are the same asthose in the case of the above-described embodiment 18.

FIG. 50 is a block diagram showing an outline configuration of anoptical pickup in an embodiment 20 of the present invention. A differentpoint from the above-described embodiments 17 through 19 is a correctiondevice 401 to correct even aberration component which originates inmanufacture error of an object lens is provided.

As a manufacture error of a glass-mold-type lens of aboth-side-aspherical type, a paraxial curvature radius deviation on eachside, an aspherical shape deviation on each side, a thickness deviation,variation in the lens material, a shift between each surface, and a tiltbetween each side are expected. Among these, the variation in a paraxialcurvature radius on each side, thickness deviation, and materialvariation can act as main factors of the even aberration. If thereoccurs such an even aberration, the shape of the light spot formed onthe recording surface may deteriorate.

In the optical pickup with an even aberration detection device in theembodiment 20 of the present invention, as shown in FIG. 50, asemiconductor laser 101 having an emission wavelength: 407±10 nm isused. As an object lens 106, any one of those described above as theembodiments 13 and 14 is used.

As shown in FIG. 50, an even aberration correction device 401 correctsthe even aberration, while the even aberration detraction device 402detects a lens manufacture error.

In case a lens manufacture error occurs, the even aberration occuraccordingly, and the shape of the light spot formed on the recordingsurface deteriorates. The thus-occurring aberration makes the wavefrontof return beam distorted, and also, an aberration occurs on the beamgoing toward the light-receiving device 109 through the detection lens108.

FIG. 51A shows this state, and when the even aberration occurs in thereturn beam incident onto the detection lens 108 from the left-hand sidein the figure, delay of wavefront occurs symmetrically with respect tothe optical axis to the standard wavefront of the return beam. As aresult, the position at which the thus-delayed wavefront is focused isdefocused with respect to the focus point of the standard wavefront.Then, it is possible to know the wavefront occurrence state by takingout the difference of the delayed wavefront and the advanced wavefront,i.e., by detecting the focal state.

For example, as the aberration detecting device 402 shown in FIG. 50, abeam course separating device such as a hologram device, a beamsplitter, or the like, or timing control device such as a light crystalshutter, and, also, a light-receiving device as shown in FIG. 51B havingits light-receiving area divided into areas A and B, are used. Byanalyzing the photo detecting outputs of the respective areas A and B,the even aberration can be detected.

Since the even aberration detected by the aberration detection device402 originates in the manufacture error of the lens, the lensmanufacture error can be known by detecting the aberration on the returnbeam as mentioned above. It becomes then possible to correct the evenaberration based on the thus-detected lens manufacture error, and thusto form a proper light spot on the recording surface. According to theembodiment 20, the aberration detected is given as an aberration signalacquired by appropriately combining the photoelectric output signalsfrom the respective areas A and B of the light-receiving device 109.

Moreover, the aberration correction device 401 in the embodiment 20includes two lenses and separation adjustment device (not shown) toadjust the separation between these lenses. Two lenses are a positivelens and a negative lens. Although the negative lens is arranged at thelight source side in the example shown in the figure, the positive lensmay instead be disposed at the light source side.

By changing the separation between the positive and negative lenses ofthe aberration correcting device 401, it is possible to cause an evenaberration to occur in the beam passing through the aberrationcorrecting device 401 toward the object lens 106. Then, the thus-createdeven aberration is used for canceling out the even aberration occurringdue to the manufacture error of the object lens 106.

It is assumed that the wavefront aberration which gives the evenaberration which originates in the manufacture error of the object lens106 detected by the aberration detection device 402 is as shown in FIG.51C. FIG. 51D shows this wavefront aberration as a 2-dimensional curve.The separation between the positive and negative lenses is controlled onthe beam incident onto the object lens 106 from the light source side sothat the divergent state in the beam be controlled appropriately.Thereby, as shown in FIG. 51E, the wavefront aberration is remarkablycorrected.

Specifically, for this purpose, beforehand the separation between thetwo lenses in the aberration correction device 401 is set so that theabove-mentioned aberration signal becomes 0 in case the object lens 106has an approximately design median. Then, in case an aberration occurson the actual object lens 106 assembled, the lens separation should becontrolled so that the aberration signal become 0.

In addition, either one of each of both of the positive lens and thenegative lens of the aberration correction devices 401 may have aconfiguration of a plurality of lenses.

FIG. 52A is a block diagram showing an outline configuration of anoptical pickup in an embodiment 21 of the present invention. A point inthat the embodiment 21 differs from the above-descried embodiment 20 isa point that an even aberration correction device 501 includes a liquidcrystal device and a voltage control device (not shown) to drive this.

As shown in FIG. 52B, in the liquid crystal device, at least onetransparent electrode is divided into concentric circular zones, and aconfiguration is made therein such that a voltage can be appliedindependently between the electrode portion of each concentric circularzone and a common electrode. Thereby, the refractive index n of theliquid crystal of each electrode portion can be freely controlled in arange from n1 to n2 by controlling this voltage.

By controlling the refractive index n, it is possible to create a beampath length difference: Δn·d (Δn stands for refractive index difference,and d stands for the cell thickness of the liquid crystal) for the beampart passing through each zone of the liquid crystal device. Thus, it ispossible to create phase difference: Δn·d (2π/λ), where λ stands for theoperating wavelength.

It is assumed that wavefront aberration which gives the even aberrationwhich originates in the manufacture error of the object lens 106detected by the aberration detection device 502 is as shown in FIG. 51C.The solid line of the upper portion of FIG. 53A shows this wavefrontaberration as a 2-dimensional curve.

Then, with respect to this wavefront aberration, the voltage applied toeach concentric circular zone electrode portion of the liquid crystaldevice is adjusted so that the phase difference shown in the dashed lineof the lower portion of FIG. 53A be given to the beam incident onto theobject lens 106 from the light source side. Thereby, the above-mentionedwavefront aberration can be cancelled out by the thus-created delay inthe wavefront on each portion of the beam which passes through theliquid crystal device. FIG. 53B shows the sum total of the solid line(wavefront aberration) and the dashed line (delay in the wavefront bythe liquid crystal device) shown in FIG. 53A, i.e., the wavefrontaberration after the correction. As can be seen clearly therefrom, thewavefront aberration is remarkably corrected.

In addition, a spherical aberration may occur accompanying a deviationof the substrate thickness of an optical recording medium in an opticalpickup which carries out recording, reproduction, or deletion on anoptical recording medium with the operating wavelength: 407±10 nm andNA: 0.85. That is, the spherical aberration accompanying a deviation ofthe substrate thickness becomes large in proportion to the first powerof the wavelength and to the forth power of NA, while controllingmanufacture error within ±10 micrometers in the substrate thickness isunrealistic on the actual optical pickup. Accordingly, it is necessaryto correct the aberration accompanying a thickness deviation in theoptical recording medium. Japanese patent No. 2502884, Japaneselaid-open patent application No. 2000-131603, Japanese patent No.3067665, Japanese laid-open patent application No. 9-128785, etc.disclose devices to perform correction on such an aberration due tosubstrate thickness deviation. Then, with utilization of such a knownscheme, it is possible to correct the even aberration resulting from theabove-mentioned lens manufacture error, together with applying aspherical aberration correction device for performing theabove-mentioned substrate thickness error correction.

In the above-described embodiments 20 and 21, the configuration isdescribed in which the aberration detection signal is created from thelight-receiving device and is used as a feedback signal for theaberration correction devices 401, 501, respectively. However, it isalso possible to create a configuration in which an ideal setting in theaberration correction device is determined appropriately withobservation of a beam transmitted by the object lens beforehand at atime of assembling work.

Moreover, a timing of correction of aberration resulting from a lensmanufacture error may be determined such as that this correctionoperation is performed at a time of a power supply start, or isperformed together with correction on the spherical aberrationaccompanying a thickness deviation of an optical recording medium at atime of loading of an optical recording medium. Alternatively, thecorrection operation may be performed at any time during recording,reproducing, or deleting operation performed on an optical recordingmedium.

Moreover, the above-mentioned aberration correcting device may also beinserted in a beam course in an optical pickup having compatibility withDVD or CD shown in FIG. 48A or 49A.

FIG. 54 is a block diagram showing an outline configuration of anoptical pickup in an embodiment 22 of the present invention. A differentpoint of the embodiment 22 from the above-described embodiments 17-19 isa point of including a correction device 601 to correct an oddaberration component which originates in manufacture error in an objectlens.

As a manufacture error of a glass mold lens with double-side asphericalsurfaces, a paraxial curvature radius deviation on each side, anaspherical surface shape deviation on each side, a thickness deviation,variation in the lens material, a shift in distance between both sides,and tilt between both sides are expected. Among these, the shift indistance between both sides and tilt between both sides may become mainfactors of the odd aberration. When there is the odd aberration, theshape of the light spot formed on the recording surface may deteriorate.

In the embodiment 22, as shown in FIG. 54, a semiconductor laser 101 hasan emission wavelength: 407±10 nm, and the object lens 106 describedabove used in either of the embodiments 13 and 14 is used.

In FIG. 54, there are provided with an odd aberration detection device601, and an odd aberration correction device 602 which detects a lensmanufacture error.

As mentioned above, when a lens manufacture error exists, the oddaberration occurs, and the shape of the light spot formed on therecording surface deteriorates. Thus, thus-occurring aberration distortsthe wavefront of the return beam, and an aberration occurs in a beamdirected toward the light-receiving device 109 through the detectionlens 108.

FIG. 55A shows this state, and when the odd aberration occurs in thereturn beam incident onto the detection lens 108 from the left-hand sidein the figure, “delay in wavefront” occurs reverse-symmetrically withrespect to the optical axis from the reference wavefront of the returnbeam. Further, imbalanced side robes occur at positions at which thedelayed wavefront is focused with respect to the positions at which thereference wavefront is focused. Then, it is possible to detect thesituation of wavefront aberration by detecting the difference betweenthe delayed wavefront and the advanced wavefront, i.e., by detecting thefocal state.

For example, aberration included in the return beam is detectable byanalyzing the light-receiving output of each area A and B shown in FIG.55B, by using a beam separating device such as a hologram device, a beamsplitter, or a device to shift an incidence timing such as a liquidcrystal shutter, together with a light receiving device 109 havingdivided light-receiving areas A and B as shown in the figure.

Since the odd aberration detected by the aberration detection device 502originates in the manufacture error of the lens, it is possible to knowthe lens manufacture error by detecting the aberration on the returnbeam. This is because of a correspondence relation thus occurringbetween the lens manufacture error and the thus-detected aberration onthe return beam. It becomes possible to correct the odd aberration basedon this lens manufacture error, and to form a proper light spot on therecording surface. According to the embodiment 22, the aberrationdetected is given as an aberration signal acquired by combining suitablythe photoelectric output signals from respective areas A and B of thelight-receiving device 109.

The aberration correction device 601 in the embodiment 22 shown in FIG.54 includes an object lens orientation adjustment device of a 4-axisactuator for controlling the orientation/inclination of the optical axisof the object lens with respect to the optical axis of the other opticalsystems controllable in 2-axis tilt control in addition to 2-directioncontrol for focus and tracking.

An odd aberration is created in the beam transmitted by the aberrationcorrection device 601 toward the object lens 106 as a result of the4-axis actuator of the aberration correction device 601 changing theorientation of the object lens. Then, what is necessary is to cancel outthe odd aberration occurring in connection with the manufacture error ofthe object lens by the thus-created odd aberration.

It is assumed that a wavefront aberration which gives the odd aberrationwhich originates in the manufacture error of the object lens 106detected by the aberration detection devices 602 is such as that shownin FIG. 55C. FIG. 55D shows this wavefront aberration as a 2-dimensionalcurve.

Then, the orientation of the object lens is changed with respect to thebeam incident from the light source side toward the object lens 106.Thereby, the wavefront aberration on the beam is well corrected as shownin FIG. 55E.

Specifically, for this purpose, beforehand the orientation of the objectlens is set so that the above-mentioned aberration signal becomes 0 incase the object lens 106 has an approximately design median. Then, incase an aberration occurs on the actual object lens 106 assembled, theobject lens orientation should be controlled so that the aberrationsignal become 0.

The aberration correction device may be, instead, of a 3-axis actuatorof focus, tracking and another one axis. In this case, the correctionperformance may be degraded in comparison to the case of employing the4-axis actuator.

FIG. 56A is a block diagram showing an outline configuration of anoptical pickup in an embodiment 23 of the present invention. A pointthat the embodiment 23 differs from the above-described embodiment 22 isa point that an odd aberration correction device 701 includes a liquidcrystal device and a voltage control device (not shown) to drive this.

As shown in FIG. 56B, the liquid crystal device can change therefractive-index n of the liquid crystal of each electrode portion freein a range from n1 through n2. Specifically, at least one transparentelectrode is divided rotational-symmetrically into the electrodeportions 31-38. Then, by controlling the voltage applied thereto, therefractive index of each portion can be controlled as mentioned above.

As the refractive index n is changed, phase difference: Δn·d (2π/λ) canbe created on a beam part which passes through each zone where λ standsfor the operating wavelength, by creating the beam path difference: Δn·d(Δn stands for a refractive-index change amount, and d stands for thecell thickness of the liquid crystal).

It is assumed that a wavefront aberration which gives the odd aberrationwhich originates in the manufacture error of the object lens 106detected by the aberration detection devices 602 is such as that shownin FIG. 55C. FIG. 55D shows this wavefront aberration as a 2-dimensionalcurve.

Then, the voltage applied to each portion of the liquid crystalelectrode is controlled so that the phase difference shown by a brokencurve shown in FIG. 57A is created in the beam incident from the lightsource side toward the object lens 106. Thereby, it is possible tocancel out the above-mentioned wavefront aberration thanks to thethus-created delay on a beam part passing through each zone of theliquid crystal device. Then, the wavefront aberration on the beam iswell corrected as shown in FIG. 57B in comparison to the original oneindicated by the solid curve shown in FIG. 57A.

There may occur a coma aberration accompanying a tilt deviation of anoptical recording medium in an optical pickup. Generally, it isnecessary to expect around ±1 degrees as a tilt occurring at a time ofoperation in the substrate of the optical recording medium. However,such a tilt may cause the coma aberration which cannot be allowed.Accordingly, it is necessary to correct the coma aberration accompanyingsuch a tilt of the optical recording medium. Japanese laid-open patentapplications Nos. 10-91990 and 2001-110075, Japanese patent No. 3142251,Japanese laid-open patent application No. 9-128785, etc. disclosedevices to correct such a coma aberration accompanying the tilt.Therefore, it is possible that such a known coma aberration correctingdevice is incorporated into the optical pickup together with theabove-mentioned odd aberration correcting device to correct theabove-mentioned odd aberration resulting from the lens manufactureerror.

In the above-described embodiments 22 and 23, the configuration isdescribed in which the aberration detection signal is created from thelight-receiving device and is used as a feedback signal for theaberration correction devices 601, 701, respectively. However, it isalso possible to create a configuration in which an ideal setting in theaberration correction device is determined with observation of a beamtransmitted by the object lens beforehand at a time of assembling work.

Moreover, a timing of correction of aberration resulting from a lensmanufacture error may be determined such as that this correctionoperation is performed at a time of a power supply start, or isperformed together with correction on the spherical aberrationaccompanying a thickness deviation of an optical recording medium at atime of loading of an optical recording medium. Alternatively, thecorrection operation may be performed at any time during recording,reproducing, or deleting operation performed on an optical recordingmedium.

Moreover, the above-mentioned aeration correcting device may also beinserted in a beam course in an optical pickup having compatibility withDVD or CD shown in FIG. 48A or 49A.

Especially, the coma aberration accompanying a tilt on the substrate ofan optical recording medium becomes larger in proportion to the −1stpower of the operating wavelength, to the 1st power of the substratethickness, and to the 3rd power of NA. However, the above-mentioned comaaberration correcting device is not necessary for CD, but is necessaryfor DVD, generally. Then, there is a possibility of it becomingunnecessary in the case of “operating wavelength: 407 nm, substratethickness: 0.1 mm, and NA: 0.85” as the coma aberration may not causeseries problem in comparison to the case of DVD.

In order to provide a configuration suitable to the above-mentionedsituation, in the configuration shown in FIG. 48A which can deal notonly with DVD but also with a new optical recording medium of operatingwavelength: 407 nm, substrate thickness; 0.1 mm and NA: 0.85, theaberration correcting device is configured such that it functions as thecoma aberration correcting device for correcting a coma aberrationoccurring due to a tilt of the substrate of the optical recording mediumin dealing with DVD while it functions as thelens-manufacture-error-originating aberration correcting device in caseof dealing with the new optical recording medium of operatingwavelength: 407 nm, substrate thickness: 0.1 mm, and NA: 0.85.

FIG. 58 is an internal perspective view showing an outline configurationof an optical information processing device in another embodiment of thepresent invention. The optical information processing device 210performs information recording, reproduction, or deletion on an opticalrecording medium 220 using an optical pickup 211. The optical recordingmedium 220 is of a disk shape, and is held by a cartridge 221 as aprotection case. The optical recording medium 220 is loaded into theoptical information processing device 210 together with the cartridge221 according to the arrow A. Then, it is rotated by a spindle motor213, and then, the optical pickup 211 performs information recording,reproduction, or deletion.

As the optical pickup 211, any one of the above-described embodiments 1through 23 is used. Thereby, it is possible to achieve satisfactoryperformance of processing the optical recording media with therespective operating wavelengths.

Further, the present invention is not limited to the above-describedembodiments, and variations and modifications may be made withoutdeparting from the basic concepts of the present invention.

The present application is based on Japanese priority applications Nos.2001-317913, 2002-051697 and 2001-308716, filed on Oct. 16, 2001, Feb.27, 2002 and Oct. 4, 2001, respectively, the entire contents of whichare hereby incorporated by reference.

1. An object lens for an infinite-type optical pickup which performsrecording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 650±20 nm, wherein: saidobject lens is used for focusing the beam onto a recording surface ofthe optical recording medium through the incident side substrate thereofso as to form a light spot on said recording surface so as to performthe information recording/reproducing/deletion; said object lens has aconfiguration of a single lens, with aspherical surface on each of bothsides thereof, and has a numerical aperture NA falling within a rangeof:0.65<NA<0.75; and said object lens has a configuration satisfying thefollowing conditional formulas:1.2nd−1.1<R1/f≦1.3nd−1.2  (1)0.37nd−0.14<WD/f≦0.39nd−0.04  (2) where: R1 denotes a paraxial curvatureradius of the surface on the light source side; WD denotes a workingdistance; nd denotes a refractive index of a lens material with respectto a d-line; and f denotes a focal length.
 2. The object lens as claimedin claim 1, wherein: said object lens has a configuration furthersatisfying the following conditional formulas:vd≦60  (3)1.5≦nd  (4) where vd denotes Abbe's number of the lens material withrespect to the d-line.
 3. An object lens for an infinite-type opticalpickup which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 650±20 nm,wherein: said object lens is used for focusing the beam onto a recordingsurface of the optical recording medium through the incident sidesubstrate thereof so as to form a light spot on said recording surfaceso as to perform the information recording/reproducing/deletion; saidobject lens has a configuration of a single lens, with asphericalsurface on each of both sides thereof, and has a numerical aperture NAfalling within a range of:0.75≦NA<0.85; and said object lens has a configuration satisfying thefollowing conditional formulas:1.0nd−0.7<R1/f≦1.2nd−1.1  (5)0.33nd−0.18<WD/f≦0.37nd−0.14  (6) where: R1 denotes a paraxial curvatureradius of the surface on the light source side; WD denotes a workingdistance; nd denotes a refractive index of a lens material with respectto a d-line; and f denotes a focal length.
 4. The object lens as claimedin claim 3, wherein: said object lens has a configuration furthersatisfying the following conditional formulas:vd≦60  (7)1.6≦nd  (8) where vd denotes Abbe's number of the lens material withrespect to the d-line.
 5. An object lens for an infinite-type opticalpickup which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 650±20 nm,wherein: said object lens is used for focusing the beam onto a recordingsurface of the optical recording medium through the incident sidesubstrate thereof so as to form a light spot on said recording surfaceso as to perform the information recording/reproducing/deletion; saidobject lens has a configuration of a single lens, with asphericalsurface on each of both sides thereof, and has a numerical aperture NAfalling within a range of:0.85≦NA; and said object lens has a configuration satisfying thefollowing conditional formulas:R1/f≦1.0nd−0.7  (9)WD/f≦0.33nd−0.18  (10) where: R1 denotes a paraxial curvature radius ofthe surface on the light source side; WD denotes a working distance; nddenotes a refractive index of the lens material with respect to thed-line; and f denotes the focal length.
 6. The object lens as claimed inclaim 5, wherein: said object lens has a configuration furthersatisfying the following conditional formulas:30≦vd≦50  (11)1.65≦nd≦1.80  (12) where vd denotes Abbe's number of the lens materialwith respect to the d-line.
 7. The object lens as claimed in claim 1,wherein: said object lens has a configuration of a meniscus lens withthe convex surface facing toward the light source side.
 8. The objectlens as claimed in claim 3, wherein: said object lens has aconfiguration of a meniscus lens with the convex surface facing towardthe light source side.
 9. The object lens as claimed in claim 5,wherein: said object lens has a configuration of a meniscus lens withthe convex surface facing toward the light source side.
 10. The objectlens as claimed in claim 2, wherein: said object lens has aconfiguration of a both-side convex lens with the surface having thesharper curvature facing toward the light source side.
 11. The objectlens as claimed in claim 4, wherein: said object lens has aconfiguration of a both-side convex lens with the surface having thesharper curvature facing toward the light source side.
 12. The objectlens as claimed in claim 6, wherein: said object lens has aconfiguration of a both-side convex lens with the surface having thesharper curvature facing toward the light source side.
 13. An objectlens for an infinite-type optical pickup which performs recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 5 0.1 mm with abeam having a wavelength of 407±10 nm, wherein: said object lens is usedfor focusing the beam onto a recording surface of the optical recordingmedium through the incident side substrate thereof so as to form a lightspot on said recording surface so as to perform the informationrecording/reproducing/deletion; said object lens has a configuration ofa single lens, with aspherical surface on each of both sides thereof,and has a numerical aperture NA falling within a range of:0.65≦NA<0.75; and said object lens has a configuration satisfying thefollowing conditional formulas:1.2nd−1.1<R1/f≦1.3rd−1.2  (13)0.37nd−0.14<WD/f≦0.39nd−0.04  (14) where: R1 denotes a paraxialcurvature radius of the surface on the light source side; WD denotes aworking distance; nd denotes a refractive index of a lens material withrespect to a d-line; and f denotes a focal length.
 14. The object lensas claimed in claim 13, wherein: said object lens has a configurationfurther satisfying the following conditional formulas:vd≦60  (15)1.5≦nd  (16) where vd denotes Abbe's number of the lens material withrespect to the d-line.
 15. An object lens for an infinite-type opticalpickup which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407±10 nm, 5wherein: said object lens is used for focusing the beam onto a recordingsurface of the optical recording medium through the incident sidesubstrate thereof so as to form a light spot on said recording surfaceso as to perform the information recording/reproducing/deletion; saidobject lens has a configuration of a single lens, with asphericalsurface on each of both sides thereof, and has a numerical aperture NAfalling within a range of:0.75<NA<0.85; and said object lens has a configuration satisfying thefollowing conditional formulas:1.0nd−0.7<R1/f≦1.2nd−1.1  (17)0.33nd−0.18<WD/f≦0.37nd−0.14  (18) where: R1 denotes a paraxialcurvature radius of the surface on the light source side; WD denotes aworking distance; nd denotes a refractive index of a lens material withrespect to a d-line; and f denotes a focal length.
 16. The object lensas claimed in claim 15, wherein: said object lens has a configurationfurther satisfying the following conditional formulas:vd≦60  (19)1.6≦nd≦1.8  (20) where vd denotes an Abbe's number of the lens materialwith respect to the d-line. 17-18. (canceled)
 19. The object lens asclaimed in claim 13, wherein: said object lens has a configuration ofmeniscus lens with the convex surface facing toward the light sourceside.
 20. The object lens as claimed in claim 15, wherein: said objectlens has a configuration of a meniscus lens with the convex surfacefacing toward the light source side.
 21. (canceled)
 22. The object lensas claimed in claim 14, wherein: said object lens has a configuration ofa both-side convex lens with the surface having the sharper curvaturefacing toward the light source side.
 23. The object lens as claimed inclaim 16, wherein: said object lens has a configuration of a both-sideconvex lens with the surface having the sharper curvature facing towardthe light source side.
 24. (canceled)
 25. An optical pickup in aninfinity system, which performs recording, reproducing or deletion ofinformation on an optical recording medium having an incident sidesubstrate with a thickness of 0.1 mm with a beam having a wavelength of650±20 nm, employing the object lens claimed in claim
 1. 26. An opticalpickup in an infinity system, which performs recording, reproducing ordeletion of information on an optical recording medium having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 650±20 nm, employing the object lens claimed in claim 3.27. An optical pickup in an infinity system, which performs recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 0.1 mm with a beamhaving a wavelength of 650±20 nm, employing the object lens claimed inclaim
 5. 28. An optical pickup in an infinity system, which performsrecording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407±20 nm, employing theobject lens claimed in claim
 13. 29. An optical pickup in an infinitysystem, which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407±20 nm,employing the object lens claimed in claim
 15. 30. (canceled)
 31. Theoptical pickup as claimed in claim 25 comprising a chromatic aberrationcorrecting device for correcting a chromatic aberration occurring due toa wavelength variation.
 32. The optical pickup as claimed in claim 26comprising chromatic aberration correcting device for correcting achromatic aberration occurring due to a wavelength variation.
 33. Theoptical pickup as claimed in claim 27 comprising chromatic aberrationcorrecting device for correcting a chromatic aberration occurring due toa wavelength variation.
 34. The optical pickup as claimed in claim 28comprising chromatic aberration correcting device for correcting achromatic aberration occurring due to a wavelength variation.
 35. Theoptical pickup as claimed in claim 29 comprising chromatic aberrationcorrecting device for correcting a chromatic aberration occurring due toa wavelength variation.
 36. (canceled)
 37. The optical pickup as claimedin claim 31, wherein: said chromatic aberration correcting devicecomprises one of a doublet lens, a resin coating provided on the objectlens and a diffraction surface provided on the object lens.
 38. Theoptical pickup as claimed in claim 32, wherein: said chromaticaberration correcting device comprises one of a doublet lens, a resincoating provided on the object lens and a diffraction surface providedon the object lens.
 39. The optical pickup as claimed in claim 33,wherein: said chromatic aberration correcting device comprises one of adoublet lens, a resin coating 5 provided on the object lens and adiffraction surface provided on the object lens.
 40. The optical pickupas claimed in claim 34, wherein: said chromatic aberration correctingdevice comprises one of a doublet lens, a resin coating provided on theobject lens and a diffraction surface provided on the object lens. 41.The optical pickup as claimed in claim 35, wherein: said chromaticaberration correcting device comprises one of a doublet lens, a resincoating provided on the object lens and a diffraction surface providedon the object lens.
 42. (canceled)
 43. The optical pickup as claimed inclaim 25, further comprising: a substrate thickness error detectingdevice which detects a substrate thickness error of the incidence sidesubstrate of the optical recording medium loaded; and a sphericalaberration correcting device which corrects a spherical aberrationoccurring due to the substrate thickness error based on the detectionresult of said substrate thickness error detecting device.
 44. Theoptical pickup as claimed in claim 26, further comprising: a substratethickness error detecting device which detects a substrate thicknesserror of the 5 incidence side substrate of the optical recording mediumloaded; and a spherical aberration correcting device which corrects aspherical aberration occurring due to the substrate thickness errorbased on the detection result of said substrate thickness errordetecting device.
 45. The optical pickup as claimed in claim 27, furthercomprising: a substrate thickness error detecting device which detects asubstrate thickness error of the incidence side substrate of the opticalrecording medium loaded; and a spherical aberration correcting devicewhich corrects a spherical aberration occurring due to the substratethickness error based on the detection result of said substratethickness error detecting device.
 46. The optical pickup as claimed inclaim 28, further comprising: a substrate thickness error detectingdevice which detects a substrate thickness error of the 5 incidence sidesubstrate of the optical recording medium loaded; and a sphericalaberration correcting device which corrects a spherical aberrationoccurring due to the substrate thickness error based on the detectionresult of said substrate thickness error detecting device.
 47. Theoptical pickup as claimed in claim 29, further comprising: a substratethickness error detecting device which detects a substrate thicknesserror of the incidence side substrate of the optical recording mediumloaded; and a spherical aberration correcting device which corrects aspherical aberration occurring due to the substrate thickness errorbased on the detection result of said substrate thickness errordetecting device.
 48. (canceled)
 49. The optical pickup as claimed inclaim 43, wherein: said spherical aberration correcting device comprisesone of a pair of positive and negative lenses with a changeableseparation thereof and a liquid crystal device having concentricelectrode patterns.
 50. The optical pickup as claimed in claim 44,wherein: said spherical aberration correcting device comprises one of apair of positive and negative lenses with a changeable separationthereof and a liquid 5 crystal device having concentric electrodepatterns.
 51. The optical pickup as claimed in claim 45, wherein: saidspherical aberration correcting device comprises one of a pair ofpositive and negative lenses with a changeable separation thereof and aliquid crystal device having concentric electrode patterns.
 52. Theoptical pickup as claimed in claim 46, wherein: said sphericalaberration correcting device comprises one of a pair of positive andnegative lenses with a changeable separation thereof and a liquidcrystal device having concentric electrode patterns.
 53. The opticalpickup as claimed in claim 47, wherein: said spherical aberrationcorrecting device comprises one of a pair of positive and negativelenses with a changeable separation thereof and a liquid crystal devicehaving concentric electrode patterns.
 54. (canceled)
 55. An opticalpickup in an infinity system, which performs recording, reproducing ordeletion of information on an optical recording medium having aplurality of recording surfaces stacked on each other, and having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 650±20 nm, comprising: a spherical aberration detectingdevice which detects a spherical aberration which differs according to adistance between the incident side substrate outer surface and anyrecording surface; a spherical aberration correcting device whichcorrects the spherical aberration detected by said spherical aberrationdetecting device; and the object lens claimed in claim
 1. 56. An opticalpickup in an infinity system, which performs recording, reproducing ordeletion of information on an optical recording medium having aplurality of recording surfaces stacked on each other, and having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 650±20 nm, comprising: a spherical aberration detectingdevice which detects a spherical aberration which differs according to adistance between the incident side substrate outer surface and anyrecording surface; a spherical aberration correcting device whichcorrects the spherical aberration detected by said spherical aberrationdetecting device; and the object lens claimed in claim
 3. 57. An opticalpickup in an infinity system, which performs recording, reproducing ordeletion of information on an optical recording medium having aplurality of recording surfaces stacked on each other, and having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 650±20 nm, comprising: a spherical aberration detectingdevice which detects a spherical aberration which differs according to adistance between the incident side substrate outer surface and anyrecording surface; a spherical aberration correcting device whichcorrects the spherical aberration detected by said spherical aberrationdetecting device; and the object lens claimed in claim
 5. 58. An opticalpickup in an infinity system, which performs recording, reproducing ordeletion of information on an optical recording medium having aplurality of recording surfaces stacked on each other, and having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 407±10 ma, comprising: a spherical aberration detectingdevice which detects a spherical aberration which differs according to adistance between the incident side substrate outer surface and anyrecording surface; a spherical aberration correcting device whichcorrects the spherical aberration detected by said spherical aberrationdetecting device; and the object lens claimed in claim
 13. 59. Anoptical pickup in an infinity system, which performs recording,reproducing or deletion of information on an optical recording mediumhaving a plurality of recording surfaces stacked on each other, andhaving an incident side substrate with a thickness of 0.1 mm with a beamhaving a wavelength of 407±10 nm, comprising: a spherical aberrationdetecting device which detects a spherical aberration which differsaccording to a distance between the incident side substrate outersurface and any recording surface; a spherical aberration correctingdevice which corrects the spherical aberration detected by saidspherical aberration detecting device; and the object lens claimed inclaim
 15. 60. An optical pickup in an infinity system, which performsrecording, reproducing or deletion of information on an opticalrecording medium having a plurality of recording surfaces stacked oneach other, and having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407±10 nm, 20 comprising: aspherical aberration detecting device which detects a sphericalaberration which differs according to a distance between the incidentside substrate outer surface and any recording surface; a sphericalaberration correcting device which corrects the spherical aberrationdetected by said spherical aberration detecting device; and the objectlens claimed in claim
 17. 61. The optical pickup as claimed in claim 55,further comprising a chromatic aberration correcting device whichcorrects a chromatic aberration occurring due to a wavelength variation.62. The optical pickup as claimed in claim 56, further comprising achromatic aberration correcting device which corrects a chromaticaberration occurring due to a wavelength variation.
 63. The opticalpickup as claimed in claim 57, further comprising a chromatic aberrationcorrecting device which corrects a chromatic aberration occurring due toa wavelength variation.
 64. The optical pickup as claimed in claim 58,further comprising a chromatic aberration correcting device whichcorrects a chromatic aberration occurring due to a wavelength variation.65. The optical pickup as claimed in claim 59, further comprising achromatic aberration correcting device which corrects a chromaticaberration occurring due to a wavelength variation.
 66. The opticalpickup as claimed in claim 60, further comprising a chromatic aberrationcorrecting device which corrects a chromatic aberration occurring due toa wavelength variation.
 67. The optical pickup as claimed in claim 31,further comprising a spherical aberration correcting device, saidchromatic aberration correcting device and said spherical aberrationcorrecting device being integrated together.
 68. The optical pickup asclaimed in claim 32, further comprising a spherical aberrationcorrecting device, said chromatic aberration correcting device and saidspherical aberration correcting device being integrated together. 69.The optical pickup as claimed in claim 33, further comprising aspherical aberration correcting device, said chromatic aberrationcorrecting device 5 and said spherical aberration correcting devicebeing integrated together.
 70. The optical pickup as claimed in claim34, further comprising a spherical aberration correcting device, saidchromatic aberration correcting device and said spherical aberrationcorrecting device being integrated together.
 71. The optical pickup asclaimed in claim 35, further comprising a spherical aberrationcorrecting device, said chromatic aberration correcting device and saidspherical aberration correcting device being integrated together. 72.(canceled)
 73. The optical pickup as claimed in claim 61, said chromaticaberration correcting device and said spherical aberration correctingdevice being integrated together.
 74. The optical pickup as claimed inclaim 62, said chromatic aberration correcting device and said sphericalaberration correcting device being integrated together.
 75. The opticalpickup as claimed in claim 63, said chromatic aberration correctingdevice and said spherical aberration correcting device being integratedtogether.
 76. The optical pickup as claimed in claim 64, said chromaticaberration correcting device and said spherical aberration correctingdevice being integrated together.
 77. The optical pickup as claimed inclaim 65, said chromatic aberration correcting device and said sphericalaberration correcting device being integrated together.
 78. The opticalpickup as claimed in claim 66, said chromatic aberration correctingdevice and said spherical aberration correcting device being integratedtogether.
 79. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 25. 80. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 26. 81. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 27. 82. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 28. 83. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 29. 84. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 30. 85. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 55. 86. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 56. 87. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 57. 88. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 58. 89. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 59. 90. An information processing device, performing recording,reproducing or deleing operation through the optical pickup claimed inclaim
 60. 91. An object lens in an infinite system used in an opticalpickup which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407±10 nm, with anumerical aperture NA of 0.85±0.05, wherein: said object lens has aconfiguration of a single lens, with an aspherical convex surface oneach of both sides thereof, formed in a glass-mold manner so as tosatisfy the following conditional formulas:vd≦6511.55≦ND where: vd denotes an Abbe's number of a lens material withrespect to the d-line; and nd denotes a refractive index of the lensmaterial with respect to the d-line.
 92. The object lens as claimed inclaim 91, wherein: said object lens further satisfies the followingconditional formulas:1.0nd−1.0≦R1/f≦1.0nd−0.8;1.2nd−0.75≦t/f≦1.2nd−0.5;−0.35nd+0.77≦WD/f≦−0.35nd+0.85 where: t denotes a lens centralthickness; R1 denotes a paraxial curvature radius of the surface on thelight source sides; WD denotes a working distance; and f denotes a focallength.
 93. The object lens as claimed in claim 1, further satisfyingthe following conditional formula:−0.42nd+0.82≦WD/f≦−0.42nd+0.95 wherein: said object lens is used as alens in a finite system; and said object lens is used for recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 0.6 mm with a beamhaving a wavelength of 660±10 nm, with a numerical aperture NA of0.65±0.05.
 94. The object lens as claimed in claim 1, further satisfyingthe following conditional formula:−0.35nd+0.64≦WD/f≦−0.35nd+0.72 wherein: said object lens is used as alens in a finite system; and said object lens is used for recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 1.2 mm with a beamhaving a wavelength of 780±10 nm, with a numerical aperture NA of0.50+0.05.
 95. The object lens as claimed in claim 1, further satisfyingthe following conditional formula:−0.42nd+0.82≦WD/f≦−0.42nd+0.95 wherein: said object lens is also used asa lens in a finite system; and said object lens is used for recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 0.6 mm with a beamhaving a wavelength of 660+10 nm, with a numerical aperture NA of0.65±0.05; and; further satisfying the following conditional formula:−0.35nd+0.64≦WD/f≦−0.35nd+0.72 wherein: said object lens is also used asa lens in a finite system; and said object lens is used for recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 1.2 mm with a beamhaving a wavelength of 780±10 nm, with a numerical aperture NA of0.50±0.05.
 96. The object lens as claimed in claim 93, furthercomprising: a numerical aperture control device which switches thenumerical aperture according to the operating wavelength applied. 97.The object lens as claimed in claim 94, further comprising: a numericalaperture control device which switches the numerical aperture accordingto the 5 operating wavelength applied.
 98. The object lens as claimed inclaim 95, further comprising: a numerical aperture control device whichswitches the numerical aperture according to the operating wavelengthapplied.
 99. The object lens as claimed in claim 93, further comprising:a lens having a surface with a sharper curvature on the side of theobject lens between the object lens and the light source.
 100. Theobject lens as claimed in claim 94, further comprising: a lens having asurface with a sharper curvature on the side of the object lens betweenthe 5 object lens and the light source.
 101. The object lens as claimedin claim 95, further comprising: a lens having a surface with a sharpercurvature on the side of the object lens between the object lens and thelight source.
 102. An optical pickup, which performs recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 0.1 mm with a beamhaving a wavelength of 407±10 nm, with a numerical aperture NA of0.85+0.05, employing the object lens claimed in claim 91 for focusing abeam from a light source onto a recording surface of the opticalrecording medium as a light spot.
 103. An optical pickup, which performsrecording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407±10 nm, with a numericalaperture NA of 0.85±0.05, and, also an optical recording medium havingan incident side substrate with a thickness of 0.6 mm with a beam havinga wavelength of 660+10 nm, with a numerical aperture NA of 0.65±0.05,employing the object lens claimed in claim 93 for focusing a beam from alight source onto a recording surface of the optical recording medium asa light spot.
 104. An optical pickup, which performs recording,reproducing or deletion of information on an optical recording mediumhaving an incident side substrate with a thickness of 0.1 mm with a beamhaving a wavelength of 407±10 nm, with a numerical aperture NA of0.85+0.05, and, also an optical recording medium having an incident sidesubstrate with a thickness of 0.6 mm with a beam having a wavelength of660±10 nm, with a numerical aperture NA of 0.65±0.05, employing theobject lens claimed in claim 95 for focusing a beam from a light sourceonto a recording surface of the optical recording medium as a lightspot.
 105. An optical pickup, which performs recording, reproducing ordeletion of information on an optical recording medium having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 407+10 nm, with a numerical aperture NA of 0.85±0.05, and,also an optical recording medium having an incident side substrate witha thickness of 1.2 mm with a beam having a wavelength of 780±10 nm, witha numerical aperture NA of 0.50±0.05, employing the object lens claimedin claim 94 for focusing a beam from a light source onto a recordingsurface of the optical recording medium as a light spot.
 106. An opticalpickup, which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407+10 nm, with anumerical aperture NA of 0.85±0.05, and, also an optical recordingmedium having an incident side substrate with a thickness of 1.2 mm witha beam having a wavelength of 780±10 nm, with a numerical aperture NA of0.50±0.05, employing the object lens claimed in claim 95 for focusing abeam from a light source onto a recording surface of the opticalrecording medium as a light spot.
 107. An optical pickup, for performingrecording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407±10 nm, with a numericalaperture NA of 0.85±0.05, also an optical recording medium having anincident side substrate with a thickness of 0.6 mm with a beam having awavelength of 660+10 nm, with a numerical aperture NA of 0.65±0.05, and,also an optical recording medium having an incident side substrate witha thickness of 1.2 mm with a beam having a wavelength of 780±10 nm, witha numerical aperture NA of 0.50±0.05, employing the object lens claimedin claim 93 for focusing a beam from a light source onto a recordingsurface of the optical recording medium as a light spot.
 108. An opticalpickup, which performs recording, reproducing or deletion of informationon an optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407+10 nm, with anumerical aperture NA of 0.85±0.05, also an optical recording mediumhaving an incident side substrate with a thickness of 0.6 mm with a beamhaving a wavelength of 660±10 nm, with a numerical aperture NA of0.65±0.05, and, also an optical recording medium having an incident sidesubstrate with a thickness of 1.2 mm with a beam having a wavelength of780+10 nm, with a numerical aperture NA of 0.50+0.05, employing theobject lens claimed in claim 94 for focusing a beam from a light sourceonto a recording surface of the optical recording medium as a lightspot.
 109. An optical pickup, which performs recording, reproducing ordeletion of information on an optical recording medium having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 407±10 nm, with a numerical aperture NA of 0.85±0.05, alsoan optical recording medium having an incident side substrate with athickness of 0.6 mm with a beam having a wavelength of 660+10 nm, with anumerical aperture NA of 0.65±0.05, and, also an optical recordingmedium having an incident side substrate with a thickness of 1.2 mm witha beam having a wavelength of 780±10 nm, with a numerical aperture NA of0.50+0.05, employing the object lens claimed in claim 95 for focusing abeam from a light source onto a recording surface of the opticalrecording medium as a light spot.
 110. The optical pickup as claimed inclaim 102, further comprising: a first correcting device to correct aneven aberration component; and a first detecting device to detect theeven aberration component.
 111. The optical pickup as claimed in claim110, wherein said first correcting device is disposed between saidobject lens and the light source and is used to change a divergencestate of an incident beam of the object lens.
 112. The optical pickup asclaimed in claim 110, wherein said first correcting device is disposedbetween said object lens and the light source, and creates a phasedifference concentrically in a beam reflected or transmitted thereby.113. The optical pickup as claimed in claim 110, wherein said firstcorrecting device corrects a spherical aberration.
 114. The opticalpickup as claimed in claim 102, further comprising: a second correctingdevice to correct an odd aberration component; and a second detectingdevice to detect the odd aberration component.
 115. The optical pickupas claimed in claim 114, wherein said second correcting device isdisposed between said object lens and the light source and is used tocause an incident beam of the object lens to incline with respect to theoptical axis of said lens.
 116. The optical pickup as claimed in claim114, wherein said second correcting device is disposed between saidobject lens and the light source, and creates a phase differencestepwise in a beam reflected or transmitted thereby.
 117. The opticalpickup as claimed in claim 114, wherein said second correcting devicecorrects a coma aberration.
 118. An optical information processingdevice, which performs, using an optical pickup, recording, reproducingor deletion of information on an optical recording medium having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 407±10 nm, with a numerical aperture NA of 0.85±0.05, andalso on an optical recording medium having an incident side substratewith a thickness of 0.6 mm with a beam having a wavelength of 660±10 nm,with a numerical aperture NA of 0.65±0.05, wherein a configuration ismade in said optical pickup such that an incident beam of the objectlens is made in an infinite system in case of dealing with the opticalrecording medium having the incident side substrate with the thicknessof 0.1 mm with the beam having the wavelength of 407±10 nm, with thenumerical aperture NA of 0.85+0.05, while the incident beam of theobject lens is made in a finite system in case of dealing with theoptical recording medium having the incident side substrate with thethickness of 0.6 mm with the beam having the wavelength of 660±10 nm,with the numerical aperture NA of 0.65+0.05.
 119. An optical informationprocessing device, which performs, by using an optical pickup,recording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407+10 nm, with a numericalaperture NA of 0.85±0.05, and also an optical recording medium having anincident side substrate with a thickness of 1.2 mm with a beam having awavelength of 780±10 nm, with a numerical aperture NA of 0.50±0.05,wherein a configuration is made in said optical pickup such that anincident beam of the object lens is made in an infinite system indealing with the optical recording medium having the incident sidesubstrate with the thickness of 0.1 m with the beam having thewavelength of 407+10 nm, with the numerical aperture NA of 0.85+0.05,while the incident beam of the object lens is made in a finite system indealing with the optical recording medium having the incident sidesubstrate with the thickness of 1.2 mm with the beam having thewavelength of 780±10 nm, with the numerical aperture NA of 0.50±0.05.120. An optical information processing device, which performs, by usingan optical pickup, recording, reproducing or deletion of information onan optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407±10 nm, with anumerical aperture NA of 0.85+0.05, also an optical recording mediumhaving an incident side substrate with a thickness of 0.6 mm with a beamhaving a wavelength of 660±10 nm, with a numerical aperture NA of0.65+0.05, and also an optical recording medium having an incident sidesubstrate with a thickness of 1.2 mm with a beam having a wavelength of780±10 nm, with a numerical aperture NA of 0.50±0.05, wherein aconfiguration is made in said optical pickup such that an incident beamof the object lens is made in an infinite system in dealing with theoptical recording medium having the incident side substrate with thethickness of 0.1 mm with the beam having the wavelength of 407±10 nm,with the numerical aperture NA of 0.85±0.05, while the incident beam ofthe object lens is made in a finite system either in dealing with theoptical recording medium having the incident side substrate with thethickness of 0.6 mm with the beam having the wavelength of 660±10 nm,with the numerical aperture NA of 0.65±0.05, or in dealing with theoptical recording medium having the incident side substrate with thethickness of 1.2 mm with the beam having the wavelength of 780+10 nm,with the numerical aperture NA of 0.50±0.05.
 121. An optical informationprocessing device, which performs, by using an optical pickup,recording, reproducing or deletion of information on an opticalrecording medium having an incident side substrate with a thickness of0.1 mm with a beam having a wavelength of 407±10 nm, with a numericalaperture NA of 0.85±0.05, and also an optical recording medium having anincident side substrate with a thickness of 0.6 mm with a beam having awavelength of 660+10 nm, with a numerical aperture NA of 0.65+0.05,comprising: a numerical aperture control device to control the numericalaperture in said optical pickup, by which the numerical aperture is made0.85+0.05 on the operating wavelength of 407±10 nm, while the numericalaperture is made 0.65±0.05 on the operating wavelength of 660±10 nm.122. An optical information processing device, which performs, by usingan optical pickup, recording, reproducing or deletion of information onan optical recording medium having an incident side substrate with athickness of 0.1 mm with a beam having a wavelength of 407±10 nm, with anumerical aperture NA of 0.85+0.05, and also an optical recording mediumhaving an incident side substrate with a thickness of 1.2 mm with a beamhaving a wavelength of 780+10 nm, with a numerical aperture NA of0.50±0.05, comprising: a numerical aperture control device to controlthe numerical aperture in said optical pickup, by which the numericalaperture is made 0.85±0.05 on the operating wavelength of 407±10 nm,while the numerical aperture is made 0.50±0.05 on the operatingwavelength of 780±10 nm.
 123. An optical information processing device,which performs, by using an optical pickup, recording, reproducing ordeletion of information on an optical recording medium having anincident side substrate with a thickness of 0.1 mm with a beam having awavelength of 407±10 nm, with a numerical aperture NA of 0.85+0.05, alsoan optical recording medium having an incident side substrate with athickness of 0.6 mm with a beam having a wavelength of 660±10 nm, with anumerical aperture NA of 0.65±0.05, and also, an optical recordingmedium having an incident side substrate with a thickness of 1.2 mm witha beam having a wavelength of 780±10 nm, with a numerical aperture of0.50±0.05, comprising: a numerical aperture control device to controlthe numerical aperture in said optical pickup, by which the numericalaperture is made 0.85±0.05 on the operating wavelength of 407+10 nm,while the numerical aperture is made 0.65±0.05 on the operatingwavelength of 660±10 nm, also while the numerical aperture is made0.50±0.05 on the operating wavelength of 780+10 nm.
 124. The opticalinformation processing device as claimed in claim 118, furthercomprising a device to correct an even or odd aberration in said opticalpickup.
 125. The optical information processing device as claimed inclaim 119, further comprising a device to correct an even or oddaberration in said optical pickup.
 126. The optical informationprocessing device as claimed in claim 120, further comprising a deviceto correct an even or odd aberration in said optical pickup.
 127. Theoptical information processing device as claimed in claim 121, furthercomprising a device to correct an even or odd aberration in said opticalpickup.
 128. The optical information processing device as claimed inclaim 122, further comprising a device to correct an even or oddaberration in said optical pickup.
 129. The optical informationprocessing device as claimed in claim 123, further comprising a deviceto correct an even or odd aberration in said optical pickup.